SwePub
Sök i SwePub databas

  Extended search

Träfflista för sökning "WFRF:(Johanson Urban) "

Search: WFRF:(Johanson Urban)

  • Result 1-50 of 56
Sort/group result
   
EnumerationReferenceCoverFind
1.
  • Agemark, Maria, et al. (author)
  • Reconstitution of water channel function and 2D-crystallization of human aquaporin 8.
  • 2012
  • In: Biochimica et Biophysica Acta. - : Elsevier BV. - 0006-3002 .- 0005-2736. ; 1818:3, s. 839-850
  • Journal article (peer-reviewed)abstract
    • Among the thirteen human aquaporins (AQP0-12), the primary structure of AQP8 is unique. By sequence alignment it is evident that mammalian AQP8s form a separate subfamily distinct from the other mammalian aquaporins. The constriction region of the pore determining the solute specificity deviates in AQP8 making it permeable to both ammonia and H(2)O(2) in addition to water. To better understand the selectivity and gating mechanism of aquaporins, high-resolution structures are necessary. So far, the structure of one human aquaporin (HsAQP5) has been solved at atomic resolution. For mammalian aquaporins in general, high-resolution structures are only available for those belonging to the water-specific subfamily (including HsAQP5). Thus, it is of interest to solve structures of other aquaporin subfamily members with different solute specificities. To achieve this the aquaporins need to be overexpressed heterologously and purified. Here we use the methylotrophic yeast Pichia pastoris as a host for the overexpression. A wide screen of different detergents and detergent-lipid combinations resulted in the solubilization of functional human AQP8 protein and in well-ordered 2D crystals. It also became evident that removal of amino acids constituting affinity tags was crucial to achieve highly ordered 2D crystals diffracting to 3Å.
  •  
2.
  • Alexandersson, Erik, et al. (author)
  • Transcriptional regulation of aquaporins in accessions of Arabidopsis in response to drought stress.
  • 2010
  • In: Plant Journal. - 1365-313X. ; 61, s. 650-660
  • Journal article (peer-reviewed)abstract
    • Summary Aquaporins facilitate water transport over cellular membranes and are therefore believed to play an important role in water homeostasis. In higher plants aquaporin-like proteins, also called major intrinsic proteins (MIPs), are divided into 5 subfamilies. We have previously shown that MIP transcription in Arabidopsis thaliana generally is down-regulated in leaves upon drought stress, apart from two members of the Plasma membrane Intrinsic Protein (PIP) subfamily, AtPIP1;4 and AtPIP2;5, which are up-regulated. In order to assess if this regulation is general or accession-specific we monitored gene expression of all PIPs in five Arabidopsis accessions. Overall drought regulation of PIPs was well conserved for all five accessions tested suggesting a general and fundamental physiological role of this drought response. In addition, significant differences among accessions were identified for transcripts of three PIP genes. Principal component analysis showed that most of the PIP transcriptional variation during drought stress could be explained by one variable linked to leaf water content. Promoter-GUS constructs of AtPIP1;4, AtPIP2;5 and also AtPIP2;6, which is unresponsive to drought stress, had distinct expression patterns concentrated to the base of the leaf petioles and parts of the flowers. The presence of drought stress response elements within the 1.6 kb promoter regions of AtPIP1;4 and AtPIP2;5, was demonstrated by comparing transcription of the promoter reporter construct and the endogenous gene upon drought stress. Analysis by ATTED-II and other web-based bioinformatical tools showed that several of the MIPs down-regulated upon drought are strongly co-expressed, whereas AtPIP1;4, AtPIP2;5 and AtPIP2;6 are not co-expressed.
  •  
3.
  • Alexandersson, Erik, et al. (author)
  • Whole gene family expression and drought stress regulation of aquaporins
  • 2005
  • In: Plant Molecular Biology. - : Springer Science and Business Media LLC. - 1573-5028 .- 0167-4412. ; 59:3, s. 469-484
  • Journal article (peer-reviewed)abstract
    • Since many aquaporins (AQPs) act as water channels, they are thought to play an important role in plant water relations. It is therefore of interest to study the expression patterns of AQP isoforms in order to further elucidate their involvement in plant water transport. We have monitored the expression patterns of all 35 Arabidopsis AQPs in leaves, roots and flowers by cDNA microarrays, specially designed for AQPs, and by quantitative real-time reverse transcriptase PCR (Q-RT-PCR). This showed that many AQPs are pre-dominantly expressed in either root or flower organs, whereas no AQP isoform seem to be leaf specific. Looking at the AQP subfamilies, most plasma membrane intrinsic proteins (PIPs) and some tonoplast intrinsic proteins (TIPs) have a high level of expression, while NOD26-like proteins (NIPs) are present at a much lower level. In addition, we show that PIP transcripts are generally down-regulated upon gradual drought stress in leaves, with the exception of AtPIP1;4 and AtPIP2;5, which are up-regulated. AtPIP2;6 and AtSIP1;1 are constitutively expressed and not significantly affected by the drought stress. The transcriptional down-regulation of PIP genes upon drought stress could also be observed on the protein level.
  •  
4.
  • Ampah-Korsah, Henry, et al. (author)
  • Single amino acid substitutions in the selectivity filter render NbXIP1;1α aquaporin water permeable
  • 2017
  • In: BMC Plant Biology. - : Springer Science and Business Media LLC. - 1471-2229. ; 17:1, s. 61-61
  • Journal article (peer-reviewed)abstract
    • BACKGROUND: Aquaporins (AQPs) are integral membrane proteins that facilitate transport of water and/or other small neutral solutes across membranes in all forms of life. The X Intrinsic Proteins (XIPs) are the most recently recognized and the least characterized aquaporin subfamily in higher plants. XIP1s have been shown to be impermeable to water but permeable to boric acid, glycerol, hydrogen peroxide and urea. However, uncertainty regarding the determinants for selectivity and lack of an activity that is easy to quantify have hindered functional investigations. In an effort to resolve these issues, we set out to introduce water permeability in Nicotiana benthamiana XIP1;1α (NbXIP1;1α), by exchanging amino acid residues of predicted alternative aromatic/arginine (ar/R) selectivity filters of NbXIP1;1α for residues constituting the water permeable ar/R selectivity filter of AtTIP2;1.RESULTS: Here, we present functional results regarding the amino acid substitutions in the putative filters as well as deletions in loops C and D of NbXIP1;1α. In addition, homology models were created based on the high resolution X-ray structure of AtTIP2;1 to rationalize the functional properties of wild-type and mutant NbXIP1;1α. Our results favour Thr 246 rather than Val 242 as the residue at the helix 5 position in the ar/R filter of NbXIP1;1α and indicate that the pore is not occluded by the loops when heterologously expressed in Pichia pastoris. Moreover, our results show that a single amino acid substitution in helix 1 (L79G) or in helix 2 (I102H) is sufficient to render NbXIP1;1α water permeable. Most of the functional results can be rationalized from the models based on a combination of aperture and hydrophobicity of the ar/R filter.CONCLUSION: The water permeable NbXIP1;1α mutants imply that the heterologously expressed proteins are correctly folded and offer means to explore the structural and functional properties of NbXIP1;1α. Our results support that Thr 246 is part of the ar/R filter. Furthermore, we suggest that a salt bridge to an acidic residue in helix 1, conserved among the XIPs in clade B, directs the orientation of the arginine in the ar/R selectivity filter and provides a novel approach to tune the selectivity of AQPs.
  •  
5.
  • Ampah-Korsah, Henry, et al. (author)
  • The aquaporin splice variant NbXIP1;1α is permeable to boric acid and is Phosphorylated in the N-terminal domain
  • 2016
  • In: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 7:JUNE2016
  • Journal article (peer-reviewed)abstract
    • Aquaporins (AQPs) are membrane channel proteins that transport water and uncharged solutes across different membranes in organisms in all kingdoms of life. In plants, the AQPs can be divided into seven different subfamilies and five of these are present in higher plants. The most recently characterized of these subfamilies is the XIP subfamily, which is found in most dicots but not in monocots. In this article, we present data on two different splice variants (α and β) of NbXIP1;1 from Nicotiana benthamiana. We describe the heterologous expression of NbXIP1;1α and β in the yeast Pichia pastoris, the subcellular localization of the protein in this system and the purification of the NbXIP1;1α protein. Furthermore, we investigated the functionality and the substrate specificity of the protein by stopped-flow spectrometry in P. pastoris spheroplasts and with the protein reconstituted in proteoliposomes. The phosphorylation status of the protein and localization of the phosphorylated amino acids were verified by mass spectrometry. Our results show that NbXIP1;1α is located in the plasma membrane when expressed in P. pastoris, that it is not permeable to water but to boric acid and that the protein is phosphorylated at several amino acids in the N-terminal cytoplasmic domain of the protein. A growth assay showed that the yeast cells expressing the N-terminally His-tagged NbXIP1;1α were more sensitive to boric acid as compared to the cells expressing the C-terminally His-tagged isoform. This might suggest that the N-terminal His-tag functionally mimics the phosphorylation of the N-terminal domain and that the N-terminal domain is involved in gating of the channel.
  •  
6.
  • Anderberg, Hanna, et al. (author)
  • Algal MIPs, high diversity and conserved motifs
  • 2011
  • In: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 11
  • Journal article (peer-reviewed)abstract
    • Background: Major intrinsic proteins (MIPs) also named aquaporins form channels facilitating the passive transport of water and other small polar molecules across membranes. MIPs are particularly abundant and diverse in terrestrial plants but little is known about their evolutionary history. In an attempt to investigate the origin of the plant MIP subfamilies, genomes of chlorophyte algae, the sister group of charophyte algae and land plants, were searched for MIP encoding genes. Results: A total of 22 MIPs were identified in the nine analysed genomes and phylogenetic analyses classified them into seven subfamilies. Two of these, Plasma membrane Intrinsic Proteins (PIPs) and GlpF-like Intrinsic Proteins (GIPs), are also present in land plants and divergence dating support a common origin of these algal and land plant MIPs, predating the evolution of terrestrial plants. The subfamilies unique to algae were named MIPA to MIPE to facilitate the use of a common nomenclature for plant MIPs reflecting phylogenetically stable groups. All of the investigated genomes contained at least one MIP gene but only a few species encoded MIPs belonging to more than one subfamily. Conclusions: Our results suggest that at least two of the seven subfamilies found in land plants were present already in an algal ancestor. The total variation of MIPs and the number of different subfamilies in chlorophyte algae is likely to be even higher than that found in land plants. Our analyses indicate that genetic exchanges between several of the algal subfamilies have occurred. The PIP1 and PIP2 groups and the Ca2+ gating appear to be specific to land plants whereas the pH gating is a more ancient characteristic shared by all PIPs. Further studies are needed to discern the function of the algal specific subfamilies MIPA-E and to fully understand the evolutionary relationship of algal and terrestrial plant MIPs.
  •  
7.
  • Anderberg, Hanna, et al. (author)
  • Annotation of Selaginella moellendorffii Major Intrinsic Proteins and the Evolution of the Protein Family in Terrestrial Plants.
  • 2012
  • In: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 3
  • Journal article (peer-reviewed)abstract
    • Major intrinsic proteins (MIPs) also called aquaporins form pores in membranes to facilitate the permeation of water and certain small polar solutes across membranes. MIPs are present in virtually every organism but are uniquely abundant in land plants. To elucidate the evolution and function of MIPs in terrestrial plants, the MIPs encoded in the genome of the spikemoss Selaginella moellendorffii were identified and analyzed. In total 19 MIPs were found in S. moellendorffii belonging to 6 of the 7 MIP subfamilies previously identified in the moss Physcomitrella patens. Only three of the MIPs were classified as members of the conserved water specific plasma membrane intrinsic protein (PIP) subfamily whereas almost half were found to belong to the diverse NOD26-like intrinsic protein (NIP) subfamily permeating various solutes. The small number of PIPs in S. moellendorffii is striking compared to all other land plants and no other species has more NIPs than PIPs. Similar to moss, S. moellendorffii only has one type of tonoplast intrinsic protein (TIP). Based on ESTs from non-angiosperms we conclude that the specialized groups of TIPs present in higher plants are not found in primitive vascular plants but evolved later in a common ancestor of seed plants. We also note that the silicic acid permeable NIP2 group that has been reported from angiosperms appears at the same time. We suggest that the expansion of the number MIP isoforms in higher plants is primarily associated with an increase in the different types of specialized tissues rather than the emergence of vascular tissue per se and that the loss of subfamilies has been possible due to a functional overlap between some subfamilies.
  •  
8.
  • Backmark, Anna, 1979, et al. (author)
  • Affinity tags can reduce merohedral twinning of membrane protein crystals
  • 2008
  • In: Acta Crystallographica. Section D: Biological Crystallography. - 1399-0047 .- 0907-4449. ; D64, s. 1183-1186
  • Journal article (peer-reviewed)abstract
    • This work presents a comparison of the crystal packing of three eukaryotic membrane proteins: human aquaporin 1, human aquaporin 5 and a spinach plasma membrane aquaporin. All were purified from expression constructs both with and without affinity tags. With the exception of tagged aquaporin 1, all constructs yielded crystals. Two significant effects of the affinity tags were observed: crystals containing a tag typically diffracted to lower resolution than those from constructs encoding the protein sequence alone and constructs without a tag frequently produced crystals that suffered from merohedral twinning. Twinning is a challenging crystallographic problem that can seriously hinder solution of the structure. Thus, for integral membrane proteins, the addition of an affinity tag may help to disrupt the approximate symmetry of the protein and thereby reduce or avoid merohedral twinning.
  •  
9.
  • Barfod, Anders, et al. (author)
  • In Vitro Selection of RNA Aptamers Directed Against Protein E: A Haemophilus influenzae Adhesin. : a Haemophilus influenzae adhesin
  • 2014
  • In: Molecular Biotechnology. - : Springer Science and Business Media LLC. - 1559-0305 .- 1073-6085. ; 56:8, s. 714-725
  • Journal article (peer-reviewed)abstract
    • Protein E (PE) of Haemophilus influenzae is a highly conserved ubiquitous surface protein involved in adhesion to and activation of epithelial cells. The host proteins-vitronectin, laminin, and plasminogen are major targets for PE-dependent interactions with the host. To identify novel inhibitory molecules of PE, we used an in vitro selection method based on systematic evolution of ligands by exponential enrichment known as SELEX in order to select 2'F-modified RNA aptamers that specifically bind to PE. Fourteen selection cycles were performed with decreasing concentrations of PE. Sequencing of clones from the 14th selection round revealed the presence of semiconserved sequence motifs in loop regions of the RNA aptamers. Among these, three aptamers showed the highest affinity to PE in electrophoretic mobility shift assays and in dot blots. These three aptamers also inhibited the interaction of PE with vitronectin as revealed by ELISA. Moreover, pre-treatment of H. influenzae with the aptamers significantly inhibited binding of vitronectin to the bacterial surface. Biacore experiments indicated that one of the aptamers had a higher binding affinity for PE as compared to the other aptamers. Our results show that it is possible to select RNA inhibitors against bacterial adhesins using SELEX in order to inhibit interactions with target proteins.
  •  
10.
  • Carlsbecker, A, et al. (author)
  • The DAL10 gene from Norway spruce (Picea abies) belongs to a potentially gymnosperm-specific subclass of MADS-box genes and is specifically active in seed cones and pollen cones.
  • 2003
  • In: Evolution & Development. - 1525-142X. ; 5:6, s. 551-561
  • Journal article (peer-reviewed)abstract
    • Transcription factors encoded by different members of the MADS-box gene family have evolved central roles in the regulation of reproductive organ development in the flowering plants, the angiosperms. Development of the stamens and carpels, the pollen- and seed-bearing organs, involves the B- and C-organ-identity MADS-box genes. B- and C-type gene orthologs with activities specifically in developing pollen- and seed-bearing organs are also present in the distantly related gymnosperms: the conifers and the gneto-phytes. We now report on the characterization of DAL10, a novel MADS-box gene from the conifer Norway spruce, which unlike the B- and C-type conifer genes shows no distinct orthology relationship to any angiosperm gene or clade in phylogenetic analyses. Like the B- and C-type genes, it is active specifically in developing pollen cones and seed cones. In situ RNA localization experiments show DAL10 to be expressed in the cone axis, which carry the microsporophylls of the young pollen cone. In contrast, in the seed cone it is expressed both in the cone axis and in the bracts, which subtend the ovuliferous scales. Expression data and the phenotype of transgenic Arabidopsis plants expressing DAL10 suggest that the gene may act upstream to or in concert with the B- and C-type genes in the establishment of reproductive identity of developing cones.
  •  
11.
  •  
12.
  • Carlsbecker, Annelie, et al. (author)
  • The MADS-box gene DAL1 is a potential mediator of the juvenile-to-adult transition in Norway spruce (Picea abies)
  • 2004
  • In: The Plant Journal. ; 40:4, s. 546-557
  • Journal article (peer-reviewed)abstract
    • Progression through the plant life cycle involves changes in many essential features, most notably in the capacity to reproduce. The transition from juvenile vegetative and non-reproductive to an adult reproductive phase is gradual and can take many years; in the conifer Norway spruce, Picea abiea, typically 20-25 years. We present a detailed analysis of the activities of three regulatory genes with potential roles in the transition in Norway spruce: DAL1, a MADS-box gene related to the AGL6 group of genes from angiosperms, and the two LEAFY-related genes PaLFY and PaNLY. DAL1 activity is initiated in the shoots of juvenile trees at an age of 3-5 years, and then increases with age, whereas both LFY genes are active throughout the juvenile phase. The activity of DAL1 further shows a spatial pattern along the stem of the tree that parallels a similar gradient in physiolpoical and morphological features associated with maturation to the adult phase. Constitutive expression of DAL1 in transgenic Arabidopsis plants caused a dramatic attenuation of both juvenile and adult growth phases;flowers forming immediately after the embryogenic phase of development in severely affected plants. Taken together, our resulsts support the notion that DAL1 may have a regulatory role in the juvenile-to-adult transition in Norway spruce.
  •  
13.
  •  
14.
  • Corcoran, Jacob, et al. (author)
  • Endogenous insensitivity to the Orco agonist VUAA1 reveals novel olfactory receptor complex properties in the specialist fly Mayetiola destructor
  • 2018
  • In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
  • Journal article (peer-reviewed)abstract
    • Insect olfactory receptors are routinely expressed in heterologous systems for functionalcharacterisation. It was recently discovered that the essential olfactory receptor co-receptor (Orco)of the Hessian fly, Mayetiola destructor (Mdes), does not respond to the agonist VUAA1, whichactivates Orco in all other insects analysed to date. Here, using a mutagenesis-based approach weidentified three residues in MdesOrco, located in different transmembrane helices as supported by 3Dmodelling, that confer sensitivity to VUAA1. Reciprocal mutations in Drosophila melanogaster (Dmel)and the noctuid moth Agrotis segetum (Aseg) Orcos diminish sensitivity of these proteins to VUAA1.Additionally, mutating these residues in DmelOrco and AsegOrco compromised odourant receptor (OR)dependent ligand-induced Orco activation. In contrast, both wild-type and VUAA1-sensitive MdesOrcowere capable of forming functional receptor complexes when coupled to ORs from all three species,suggesting unique complex properties in M. destructor, and that not all olfactory receptor complexesare “created” equal.
  •  
15.
  • Danielson, Jonas, et al. (author)
  • Phylogeny of Major Intrinsic Proteins
  • 2010
  • In: Advances in Experimental Medicine and Biology. - 0065-2598. ; 679, s. 19-32
  • Journal article (peer-reviewed)abstract
    • Major intrinsic proteins (MIPs) form a large superfamily of proteins that can be divided into different subfamilies and groups according to phylogenetic analyses. Plants encode more MIPs than other organisms and seven subfamilies have been defined, whereof the Nodulin26-like major intrinsic proteins (NIPs) have been shown to permeate metalloids. In this chapter we review the phylogeny of MIPs in general and especially of the plant MIPs. We also identify bacterial NIP-like MIPs and discuss the evolutionary implications of this finding regarding the origin and ancestral transport specificity of the NIPs.
  •  
16.
  • Danielson, Jonas, et al. (author)
  • Unexpected complexity of the Aquaporin gene family in the moss Physcomitrella patens
  • 2008
  • In: BMC Plant Biology. - : Springer Science and Business Media LLC. - 1471-2229. ; 8:45
  • Journal article (peer-reviewed)abstract
    • Background: Aquaporins, also called major intrinsic proteins (MIPs), constitute an ancient superfamily of channel proteins that facilitate the transport of water and small solutes across cell membranes. MIPs are found in almost all living organisms and are particularly abundant in plants where they form a divergent group of proteins able to transport a wide selection of substrates. Results: Analyses of the whole genome of Physcomitrella patens resulted in the identification of 23 MIPs, belonging to seven different subfamilies, of which only five have been previously described. Of the newly discovered subfamilies one was only identified in P. patens (Hybrid Intrinsic Protein, HIP) whereas the other was found to be present in a wide variety of dicotyledonous plants and forms a major previously unrecognized MIP subfamily (X Intrinsic Proteins, XIPs). Surprisingly also some specific groups within subfamilies present in Arabidopsis thaliana and Zea mays could be identified in P. patens. Conclusion: Our results suggest an early diversification of MIPs resulting in a large number of subfamilies already in primitive terrestrial plants. During the evolution of higher plants some of these subfamilies were subsequently lost while the remaining subfamilies expanded and in some cases diversified, resulting in the formation of more specialized groups within these subfamilies.
  •  
17.
  • Florio, Marilina, et al. (author)
  • Characterization of the Aquaporin-9 Inhibitor RG100204 In Vitro and in db/db Mice
  • 2022
  • In: Cells. - : MDPI AG. - 2073-4409. ; 11:19
  • Journal article (peer-reviewed)abstract
    • Aquaporin-9 (AQP9) is a facilitator of glycerol and other small neutral solute transmembrane diffusion. Identification of specific inhibitors for aquaporin family proteins has been difficult, due to high sequence similarity between the 13 human isoforms, and due to the limited channel surface areas that permit inhibitor binding. The few AQP9 inhibitor molecules described to date were not suitable for in vivo experiments. We now describe the characterization of a new small molecule AQP9 inhibitor, RG100204 in cell-based calcein-quenching assays, and by stopped-flow light-scattering recordings of AQP9 permeability in proteoliposomes. Moreover, we investigated the effects of RG100204 on glycerol metabolism in mice. In cell-based assays, RG100204 blocked AQP9 water permeability and glycerol permeability with similar, high potency (~5 × 10 -8 M). AQP9 channel blocking by RG100204 was confirmed in proteoliposomes. After oral gavage of db/db mice with RG100204, a dose-dependent elevation of plasma glycerol was observed. A blood glucose-lowering effect was not statistically significant. These experiments establish RG100204 as a direct blocker of the AQP9 channel, and suggest its use as an experimental tool for in vivo experiments on AQP9 function.
  •  
18.
  • Gustavsson, Sofia, et al. (author)
  • A novel plant major intrinsic protein in Physcomitrella patens most similar to bacterial glycerol channels
  • 2005
  • In: Plant Physiology. - : Oxford University Press (OUP). - 1532-2548 .- 0032-0889. ; 139:1, s. 287-295
  • Journal article (peer-reviewed)abstract
    • A gene encoding a novel fifth type of major intrinsic protein (MIP) in plants has been identified in the moss Physcomitrella patens. Phylogenetic analyses show that this protein, GlpF-like intrinsic protein (GIP1;1), is closely related to a subclass of glycerol transporters in bacteria that in addition to glycerol are highly permeable to water. A likely explanation of the occurrence of this bacterial-like MIP in P. patens is horizontal gene transfer. The expressed P. patens GIP1;1 gene contains five introns and encodes a unique C-loop extension of approximately 110 amino acid residues that has no obvious similarity with any other known protein. Based on alignments and structural comparisons with other MIPs, GIP1;1 is suggested to have retained the permeability for glycerol but not for water. Studies on heterologously expressed GIP1;1 in Xenopus laevis oocytes confirm the predicted substrate specificity. Interestingly, proteins of one of the plant-specific subgroups of MIPs, the NOD26-like intrinsic proteins, are also facilitating the transport of glycerol and have previously been suggested to have evolved from a horizontally transferred bacterial gene. Further studies on localization and searches for GIP1;1 homologs in other plants will clarify the function and significance of this new plant MIP.
  •  
19.
  • Hedfalk, Kristina, et al. (author)
  • Aquaporin gating
  • 2006
  • In: Current Opinion in Structural Biology. - : Elsevier BV. - 1879-033X .- 0959-440X. ; 16, s. 447-456
  • Research review (peer-reviewed)abstract
    • An acceleration in the rate at which new aquaporin structures are determined means that structural models are now available for mammalian AQP0, AQP1, AQP2 and AQP4, bacterial GlpF, AqpM and AQPZ, and the plant SoPIP2;1. With an apparent consensus emerging concerning the mechanism of selective water transport and proton extrusion, emphasis has shifted towards the issues of substrate selectivity and the mechanisms of aquaporin regulation. In particular, recently determined structures of plant SoPIP2;1, sheep and bovine AQP0, and Escherichia coli AQPZ provide new insights into the underlying structural mechanisms by which water transport rates are regulated in diverse organisms. From these results, two distinct pictures of 'capping' and 'pinching' have emerged to describe aquaporin gating.
  •  
20.
  • Horsefield, Rob, 1977, et al. (author)
  • High-resolution x-ray structure of human aquaporin 5
  • 2008
  • In: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 105:36, s. 13327-13332
  • Journal article (peer-reviewed)abstract
    • Human aquaporin 5 (HsAQP5)facilitates the transport of water across plasma membranes and has been identified within cells of the stomach, duodenum, pancreas, airways, lungs, salivary glands, sweat glands, eyes, lacrimal glands, and the inner ear. AQP5, like AQP2, is subject to posttranslational regulation by phosphorylation, at which point it is trafficked between intracellular storage compartments and the plasma membrane. Details concerning the molecular mechanism of membrane trafficking are unknown. Here we report the x-ray structure of HsAQP5 to 2.0-angstrom resolution and highlight structural similarities and differences relative to other eukaryotic aquaporins. A lipid occludes the putative central pore, preventing the passage of gas or ions through the center of the tetramer. Multiple consensus phosphorylation sites are observed in the structure and their potential regulatory role is discussed. We postulate that a change in the conformation of the C terminus may arise from the phosphorylation of AQP5 and thereby signal trafficking.
  •  
21.
  • Jelen, Sabina, et al. (author)
  • Aquaporin-9 Protein Is the Primary Route of Hepatocyte Glycerol Uptake for Glycerol Gluconeogenesis in Mice
  • 2011
  • In: Journal of Biological Chemistry. - 1083-351X. ; 286:52, s. 44319-44325
  • Journal article (peer-reviewed)abstract
    • It has been hypothesized that aquaporin-9 (AQP9) is part of the unknown route of hepatocyte glycerol uptake. In a previous study, leptin receptor-deficient wild-type mice became diabetic and suffered from fasting hyperglycemia whereas isogenic AQP9(-/-) knock-out mice remained normoglycemic. The reason for this improvement in AQP9(-/-) mice was not established before. Here, we show increased glucose output (by 123% +/- 36% S. E.) in primary hepatocyte culture when 0.5 mM extracellular glycerol was added. This increase depended on AQP9 because it was absent in AQP9(-/-) cells. Likewise, the increase was abolished by 25 mu M HTS13286 (IC(50) similar to 2 mu M), a novel AQP9 inhibitor, which we identified in a small molecule library screen. Similarly, AQP9 deletion or chemical inhibition eliminated glycerol-enhanced glucose output in perfused liver preparations. The following control experiments suggested inhibitor specificity to AQP9: (i) HTS13286 affected solute permeability in cell lines expressing AQP9, but not in cell lines expressing AQPs 3, 7, or 8. (ii) HTS13286 did not influence lactate-and pyruvate-dependent hepatocyte glucose output. (iii) HTS13286 did not affect glycerol kinase activity. Our experiments establish AQP9 as the primary route of hepatocyte glycerol uptake for gluconeogenesis and thereby explain the previously observed, alleviated diabetes in leptin receptor-deficient AQP9(-/-) mice.
  •  
22.
  • Johanson, Suzanne, et al. (author)
  • Enabling the return-to-work process among people with affective disorders : a multiple-case study
  • 2019
  • In: Scandinavian Journal of Occupational Therapy. - : Taylor & Francis. - 1103-8128 .- 1651-2014. ; 26:3, s. 205-218
  • Journal article (peer-reviewed)abstract
    • Background: The Individual Enabling and Support (IES) model is an adapted, supported employment program developed to meet motivational, cognitive and time-use needs of people with affective disorders. Vocational programs for this target group have been developed but more knowledge is needed about the important characteristics and perceived usefulness of the programs. The aim of this study was to illustrate the IES model and process from multiple perspectives.Methods: Five participants were included in this multiple-case study. The material comprised interviews with participants, intervention documents, memos and interviews with employment specialists. Within and cross-case analyzes and an analytical generalization were performed.Results: The cases illustrated different IES processes, and the theme; Enabling engagement in return to work (RTW) was formulated. Continuous support from the employment specialist and a focus on personal resources and motivation were essential to overcome low self-confidence regarding RTW. Motivational, cognitive and time-use strategies gave an opportunity to learn new behavior and coping strategies for job seeking, getting employed and working.Conclusion: Providing a combination of these strategies integrated with supported employment could promote self-efficacy and engagement in the RTW process among people on sick leave due to an affective disorder.
  •  
23.
  • Johanson, Suzanne, et al. (author)
  • Implementation of a novel return-to-work approach for persons with affective disorders in a traditional vocational rehabilitation context: a case study
  • 2020
  • In: International Journal of Mental Health Systems. - : Springer Science and Business Media LLC. - 1752-4458. ; 14:1
  • Journal article (peer-reviewed)abstract
    • Background The person-centred Individual Enabling and Support (IES) model is a novel return-to-work (RTW) intervention for people with affective disorders that was developed from evidence-based supported employment for persons with severe mental illness. Typically, supported employment is integrated into mental healthcare and provides a network around the service user and close collaboration with employment and insurance services and employers. Introducing integrated models into a highly sectored welfare system that includes traditional mental healthcare and vocational rehabilitation is challenging. Greater knowledge is needed to understand how facilitating or hindering factors influence this introduction. The aim of this study was to investigate essential components in implementation of the IES model. Methods A case-study was conducted and included four mental healthcare services. Data collection was comprised of semi-structured interviews with 19 key informants, documentation from meetings, and reflection notes. Analyses were performed according to directed content analysis, using the components of the Consolidated Framework of Implementation Research (CFIR) as a guiding tool. Fidelity assessments were performed at 6 and 12 months. Results Anticipating RTW support for the target group, and building collaborative relationships and a network with employment specialists that engaged staff in every organization were components that resulted in the greatest facilitation if IES implementation. Barriers consisted of difficulty in integrating employment specialists into the mental healthcare teams, insufficient engagement of first line managers, reorganization and differing perceptions of the IES model fit into a traditional vocational context. Delivery of the IES model had good fidelity. Conclusions The IES model can be implemented with good fidelity, several model advantages, and context adaptation. Team integration difficulties and negative perceptions of model fit in a traditional vocational rehabilitation context can be overcome to a certain degree, but this is insufficient for sustainable implementation on a larger scale. Policy and guidelines need to promote integrative and person-centred RTW approaches rather than a segregated stepwise approach. Further implementation studies in the traditional vocational rehabilitation context are needed.
  •  
24.
  • Johanson, Urban, et al. (author)
  • A new mutation in 16S rRNA of Escherichia coli conferring spectinomycin resistance
  • 1995
  • In: Nucleic Acids Research. - 0305-1048 .- 1362-4962. ; 23:3, s. 464-466
  • Journal article (peer-reviewed)abstract
    • We report a novel mutation, Cl 066U in 16S rRNA whichwas selected for resistance to spectinomycin, anantibiotic which inhibits ribosomal translocation. Theminimal inhibitory concentration (MIC) of spectinomycindetermined for this mutant (15 pg/ml) is greaterthan with the wild-type plasmid (5 ig/ml) but lower thanwith the well known C1192U mutation (>80 pg/ml). TheCl 066U mutation also increases the cells sensitivity tofusidic acid, another antibiotic which inhibits translationat the translocation stage, whereas C1192U isunchanged relative to the wild type. We discuss whythe acquisition of resistance to one of these drugs isoften associated with hypersensitivity to the other.
  •  
25.
  • Johanson, Urban, et al. (author)
  • A new subfamily of major intrinsic proteins in plants.
  • 2002
  • In: Molecular biology and evolution. - 0737-4038. ; 19:4, s. 456-461
  • Journal article (peer-reviewed)abstract
    • The major intrinsic proteins (MIPs) form a large protein family of ancient origin and are found in bacteria, fungi, animals, and plants. MIPs act as channels in membranes to facilitate passive transport across the membrane. Some MIPs allow small polar molecules like glycerol or urea to pass through the membrane. However, the majority of MIPs are thought to be aquaporins (AQPs), i.e., they are specific for water transport. Plant MIPs can be subdivided into the plasma membrane intrinsic protein, tonoplast intrinsic protein, and NOD26-like intrinsic protein subfamilies. By database mining and phylogenetic analyses, we have identified a new subfamily in plants, the Small basic Intrinsic Proteins (SIPs). Comparisons of sequences from the new subfamily with conserved amino acid residues in other MIPs reveal characteristic features of SIPs. Possible functional consequences of these features are discussed in relation to the recently solved structures of AQP1 and GlpF. We suggest that substitutions at conserved and structurally important positions imply a different substrate specificity for the new subfamily.
  •  
26.
  • Johanson, Urban, et al. (author)
  • Comparison of the complete sequence of the str operon in Salmonella typhimurium and Escherichia coli
  • 1992
  • In: Gene. - 0378-1119 .- 1879-0038. ; 120:1, s. 93-98
  • Journal article (peer-reviewed)abstract
    • The nucleotide (nt) sequences of the str operon in Escherichia coli K-12 and Salmonella typhimurium LT2 were completed and compared at the nt and amino acid (aa) level. The order of conservation at the nt and aa level is rpsL greater than tufA greater than rpsG greater than f usA. A striking difference is that the rpsG-encoded ribosomal protein, S7, in E. coli K-12 is 23 aa longer than in S. typhimurium. The very low (0.18) codon adaptation index of this part of the E. coli K-12-encoding gene and the unusual stop codon (UGA) suggest that this is a relatively recent extension. A trend towards a higher G+C content in fusA (gene encoding elongation factor (EF)-G) and tufA (gene encoding EF-Tu) in S. typhimurium is noted. In fusA, nt substitutions at all three positions in a codon occur at a much higher frequency than expected from the number of nt substitutions in the gene, assuming they are random and independent events. An analysis of substitutions in this and other genes suggests that the triple substitutions in fusA, and some other genes, are the result of the sequential accumulation of individual mutations, probably driven by selection pressure for particular codons or aa.
  •  
27.
  • Johanson, Urban, et al. (author)
  • Molecular analysis of FRIGIDA, a major determinant of natural variation in Arabidopsis flowering time
  • 2000
  • In: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 290:5490, s. 344-347
  • Journal article (peer-reviewed)abstract
    • Vernalization, the acceleration of flowering by a long period of cold temperature, ensures that many plants overwinter vegetatively and flower in spring. In Arabidopsis, allelic variation at the FRIGIDA (FRI) locus is a major determinant of natural variation in flowering time. Dominant alleles of FRI confer late flowering, which is reversed to earliness by vernalization. We cloned FRI and analyzed the molecular basis of the allelic variation. Most of the early-flowering ecotypes analyzed carry FRI alleles containing one of two different deletions that disrupt the open reading frame. Loss-of-function mutations at FRI have thus provided the basis for the evolution of many early-flowering ecotypes.
  •  
28.
  • Johanson, Urban, et al. (author)
  • The complete set of genes encoding major intrinsic proteins in Arabidopsis provides a framework for a new nomenclature for major intrinsic proteins in plants
  • 2001
  • In: Plant Physiology. - : Oxford University Press (OUP). - 1532-2548 .- 0032-0889. ; 126:4, s. 1358-1369
  • Journal article (peer-reviewed)abstract
    • Major intrinsic proteins (MIPs) facilitate the passive transport of small polar molecules across membranes. MIPs constitute a very old family of proteins and different forms have been found in all kinds of living organisms, including bacteria, fungi, animals, and plants. In the genomic sequence of Arabidopsis, we have identified 35 different MIP-encoding genes. Based on sequence similarity, these 35 proteins are divided into four different subfamilies: plasma membrane intrinsic proteins, tonoplast intrinsic proteins, NOD26-like intrinsic proteins also called NOD26-like MIPs, and the recently discovered small basic intrinsic proteins. In Arabidopsis, there are 13 plasma membrane intrinsic proteins, 10 tonoplast intrinsic proteins, nine NOD26-like intrinsic proteins, and three small basic intrinsic proteins. The gene structure in general is conserved within each subfamily, although there is a tendency to lose introns. Based on phylogenetic comparisons of maize (Zea mays) and Arabidopsis MIPs (AtMIPs), it is argued that the general intron patterns in the subfamilies were formed before the split of monocotyledons and dicotyledons. Although the gene structure is unique for each subfamily, there is a common pattern in how transmembrane helices are encoded on the exons in three of the subfamilies. The nomenclature for plant MIPs varies widely between different species but also between subfamilies in the same species. Based on the phylogeny of all AtMIPs, a new and more consistent nomenclature is proposed. The complete set of AtMIPs, together with the new nomenclature, will facilitate the isolation, classification, and labeling of plant MIPs from other species.
  •  
29.
  •  
30.
  • Johansson, Ingela, et al. (author)
  • The role of aquaporins in cellular and whole plant water balance
  • 2000
  • In: Biochimica et Biophysica Acta - Biomembranes. - 0005-2736. ; 1465:1-2, s. 324-342
  • Research review (peer-reviewed)abstract
    • Aquaporins are water channel proteins belonging to the major intrinsic protein (MIP) superfamily of membrane proteins. More than 150 MIPs have been identified in organisms ranging from bacteria to animals and plants. In plants, aquaporins are present in the plasma membrane and in the vacuolar membrane where they are abundant constituents. Functional studies of aquaporins have hitherto mainly been performed by heterologous expression in Xenopus oocytes. A main issue is now to understand their role in the plant, where they are likely to be important both at the cellular and at the whole plant level. Plants contain a large number of aquaporin isoforms with distinct cell type- and tissue-specific expression patterns. Some of these are constitutively expressed, whereas the expression of others is regulated in response to environmental factors, such as drought and salinity. At the protein level, regulation of water transport activity by phosphorylation has been reported for some aquaporins.
  •  
31.
  • Kirscht, Andreas, et al. (author)
  • A structural preview of aquaporin 8 via homology modeling of seven vertebrate isoforms
  • 2018
  • In: BMC Structural Biology. - : Springer Science and Business Media LLC. - 1472-6807. ; 18:1
  • Journal article (peer-reviewed)abstract
    • Background: Aquaporins (AQPs) facilitate the passage of small neutral polar molecules across membranes of the cell. In animals there are four distinct AQP subfamilies, whereof AQP8 homologues constitute one of the smallest subfamilies with just one member in man. AQP8 conducts water, ammonia, urea, glycerol and H2O2 through various membranes of animal cells. This passive channel has been connected to a number of phenomena, such as volume change of mitochondria, ammonia neurotoxicity, and mitochondrial dysfunction related to oxidative stress. Currently, there is no experimentally determined structure of an AQP8, hence the structural understanding of this subfamily is limited. The recently solved structure of the plant AQP, AtTIP2;1, which has structural and functional features in common with AQP8s, has opened up for construction of homology models that are likely to be more accurate than previous models. Results: Here we present homology models of seven vertebrate AQP8s. Modeling based on the AtTIP2;1 structure alone resulted in reasonable models except for the pore being blocked by a phenylalanine that is not present in AtTIP2;1. To achieve an open pore, these models were supplemented with models based on the bacterial water specific AQP, EcAqpZ, creating a chimeric monomeric model for each AQP8 isoform. The selectivity filter (also named the aromatic/arginine region), which defines the permeant substrate profile, comprises five amino acid residues in AtTIP2;1, including a histidine coming from loop C. Compared to AtTIP2;1, the selectivity filters of modelled AQP8s only deviates in that they are slightly more narrow and more hydrophobic due to a phenylalanine replacing the histidine from loop C. Interestingly, the models do not exclude the existence of a side pore beneath loop C similar to that described in the structure of AtTIP2;1. Conclusions: Our models concur that AQP8s are likely to have an AtTIP2;1-like selectivity filter. The detailed description of the expected configuration of residues in the selectivity filters of AQP8s provides an excellent starting point for planning of as well as rationalizing the outcome of mutational studies. Our strategy to compile hybrid models based on several templates may prove useful also for other AQPs for which structural information is limited.
  •  
32.
  • Kirscht, Andreas, et al. (author)
  • Crystal Structure of an Ammonia-Permeable Aquaporin
  • 2016
  • In: PLoS Biology. - : Public Library of Science (PLoS). - 1545-7885. ; 14:3
  • Journal article (peer-reviewed)abstract
    • Aquaporins of the TIP subfamily (Tonoplast Intrinsic Proteins) have been suggested to facilitate permeation of water and ammonia across the vacuolar membrane of plants, allowing the vacuole to efficiently sequester ammonium ions and counteract cytosolic fluctuations of ammonia. Here, we report the structure determined at 1.18 Å resolution from twinned crystals of Arabidopsis thaliana aquaporin AtTIP2;1 and confirm water and ammonia permeability of the purified protein reconstituted in proteoliposomes as further substantiated by molecular dynamics simulations. The structure of AtTIP2;1 reveals an extended selectivity filter with the conserved arginine of the filter adopting a unique unpredicted position. The relatively wide pore and the polar nature of the selectivity filter clarify the ammonia permeability. By mutational studies, we show that the identified determinants in the extended selectivity filter region are sufficient to convert a strictly water-specific human aquaporin into an AtTIP2;1-like ammonia channel. A flexible histidine and a novel water-filled side pore are speculated to deprotonate ammonium ions, thereby possibly increasing permeation of ammonia. The molecular understanding of how aquaporins facilitate ammonia flux across membranes could potentially be used to modulate ammonia losses over the plasma membrane to the atmosphere, e.g., during photorespiration, and thereby to modify the nitrogen use efficiency of plants.
  •  
33.
  • Kirscht, Andreas, et al. (author)
  • Increased Permeability of the Aquaporin SoPIP2;1 by Mercury and Mutations in Loop A
  • 2016
  • In: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 7, s. 1-11
  • Journal article (peer-reviewed)abstract
    • Aquaporins (AQPs) also referred to as Major intrinsic proteins, regulate permeability of biological membranes for water and other uncharged small polar molecules. Plants encode more AQPs than other organisms and just one of the four AQP subfamilies in Arabidopsis thaliana, the water specific plasma membrane intrinsic proteins (PIPs), has 13 isoforms, the same number as the total AQPs encoded by the entire human genome. The PIPs are more conserved than other plant AQPs and here we demonstrate that a cysteine residue, in loop A of SoPIP2;1 from Spinacia oleracea, is forming disulfide bridges. This is in agreement with studies on maize PIPs, but in contrast we also show an increased permeability of mutants with a substitution at this position. In accordance with earlier findings, we confirm that mercury increases water permeability of both wild type and mutant proteins. We report on the slow kinetics and reversibility of the activation, and on quenching of intrinsic tryptophan fluorescence as a potential reporter of conformational changes associated with activation. Hence, previous studies in plants based on the assumption of mercury as a general AQP blocker have to be reevaluated, whereas mercury and fluorescence studies of isolated PIPs provide new means to follow structural changes dynamically.
  •  
34.
  • Kjellbom, Per, et al. (author)
  • Aquaporins and water homeostasis in plants
  • 1999
  • In: Trends in Plant Science. - 1360-1385. ; 4:8, s. 308-314
  • Research review (peer-reviewed)abstract
    • Aquaporins are water channel proteins of vacuolar and plasma membranes. When opened they facilitate the passive movement of water molecules down a water potential gradient. In Arabidopsis, 30 genes have been found that code for aquaporin homologues. Some of these genes code for highly abundant constitutively expressed proteins and some are known to be temporally and spatially regulated during development and in response to stress. The water transport activity of two aquaporins is regulated at the protein level by phosphorylation and dephosphorylation. At a given time, cells express several different aquaporins, and it is probable that vacuolar and plasma membrane aquaporins acting in concert are responsible for the cytosolic osmoregulation that is necessary for maintaining normal metabolic processes. Inhibition studies of aquaporins in vivo and antisense mutant studies suggest that, in addition to cytosolic osmoregulation, aquaporins are important for the bulk flow of water in plants.
  •  
35.
  • Kukulski, W, et al. (author)
  • The 5 angstrom structure of heterologously expressed plant aquaporin SoPIP2;1
  • 2005
  • In: Journal of Molecular Biology. - : Elsevier BV. - 1089-8638 .- 0022-2836. ; 350:4, s. 611-616
  • Journal article (peer-reviewed)abstract
    • SoPIP2;1 is one of the major integral proteins in spinach leaf plasma membranes. In the Xenopus oocyte expression system its water channel activity is regulated by phosphorylation at the C terminus and in the first cytosolic loop. To assess its structure, SoPIP2;1 was heterologously expressed in Pichia pastoris as a His-tagged protein and in the non-tagged form. Both forms were reconstituted into 2D crystals in the presence of lipids. Tubular crystals and double-layered crystalline sheets of non-tagged SoPIP2;1 were observed and analyzed by cryo-electron microscopy. Crystalline sheets were highly ordered and diffracted electrons to a resolution of 2.96 angstrom. High-resolution projection maps of tilted specimens provided a 3D structure at 5 angstrom resolution. Superposition of the SoPIP2;1 potential map with the atomic model of AQP1 demonstrates the generally well conserved overall structure of water channels. Differences concerning the extracellular loop A explain the particular crystal contacts between oppositely oriented membrane sheets of SoPIP2;1 2D crystals, and may have a function in rapid volume changes observed in stomatal guard cells or mesophyll protoplasts. This crystal packing arrangement provides access to the phosphorylated C terminus as well as the loop B phosphorylation site for studies of channel gating. (c) 2005 Elsevier Ltd. All rights reserved.
  •  
36.
  • Liénard, Marjorie A., et al. (author)
  • TRPA5 encodes a thermosensitive ankyrin ion channel receptor in a triatomine insect
  • 2024
  • In: iScience. - 2589-0042. ; 27:4
  • Journal article (peer-reviewed)abstract
    • As ectotherms, insects need heat-sensitive receptors to monitor environmental temperatures and facilitate thermoregulation. We show that TRPA5, a class of ankyrin transient receptor potential (TRP) channels absent in dipteran genomes, may function as insect heat receptors. In the triatomine bug Rhodnius prolixus (order: Hemiptera), a vector of Chagas disease, the channel RpTRPA5B displays a uniquely high thermosensitivity, with biophysical determinants including a large channel activation enthalpy change (72 kcal/mol), a high temperature coefficient (Q10 = 25), and in vitro temperature-induced currents from 53°C to 68°C (T0.5 = 58.6°C), similar to noxious TRPV receptors in mammals. Monomeric and tetrameric ion channel structure predictions show reliable parallels with fruit fly dTRPA1, with structural uniqueness in ankyrin repeat domains, the channel selectivity filter, and potential TRP functional modulator regions. Overall, the finding of a member of TRPA5 as a temperature-activated receptor illustrates the diversity of insect molecular heat detectors.
  •  
37.
  • Macvanin, Mirjana, et al. (author)
  • Fusidic acid-resistant EF-G perturbs the accumulation of ppGpp
  • 2000
  • In: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 37:1, s. 98-107
  • Journal article (peer-reviewed)abstract
    • Reductions in growth rate caused by fusidic acid-resistant EF-G mutants in Salmonella typhimurium correlate strongly with increased mean cell size. This is unusual because growth rate and cell size normally correlate positively. The global transcription regulator molecule ppGpp has a role in co-ordinating growth rate and division, and its basal level normally correlates inversely with cell size at division. We show that fusidic acid-resistant EF-G mutants have perturbed ppGpp basal levels during steady-state growth and perturbed induced levels during starvation. One mutation, fusA1, associated with the slowest growth rate and largest cell size, causes a reduction in the basal level of ppGpp to one-third of that found in the wild-type strain. Other fusA mutants with intermediate or wild-type growth rates and cell sizes have either normal or increased basal levels of ppGpp. There is an inverse relationship between the basal level of ppGpp in vivo and the degree to which translation dependent on mutant EF-G is inhibited by ppGpp in vitro. This enhanced interaction between mutant EF-G and ppGpp correlates with an increased KM for GTP. Our results suggest that mutant EF-G modulates the production of ppGpp by the RelA (PSI) pathway. In conclusion, fusidic acid-resistant EF-G mutations alter the level of ppGpp and break the normal relationship between growth rate and cell size at division. It would not be surprising if other phenotypes associated with these mutants, such as loss of virulence, were also related to perturbations in ppGpp levels effected through altered transcription patterns.
  •  
38.
  •  
39.
  • Michalecka, Agnieszka, et al. (author)
  • Arabidopsis genes encoding mitochondrial type II NAD(P)H dehydrogenases have different evolutionary orgin and show distinct responses to light.
  • 2003
  • In: Plant Physiology. - : Oxford University Press (OUP). - 1532-2548 .- 0032-0889. ; 133:2, s. 642-652
  • Journal article (peer-reviewed)abstract
    • In addition to proton-pumping complex I, plant mitochondria contain several type II NAD(P)H dehydrogenases in the electron transport chain. The extra enzymes allow the nonenergy-conserving electron transfer from cytoplasmic and matrix NAD(P)H to ubiquinone. We have investigated the type II NAD(P)H dehydrogenase gene families in Arabidopsis. This model plant contains two and four genes closely related to potato (Solanum tuberosum) genes nda1 and ndb1, respectively. A novel homolog, termed ndc1, with a lower but significant similarity to potato nda1 and ndb1, is also present. All genes are expressed in several organs of the plant. Among the nda genes, expression of nda1, but not nda2, is dependent on light and circadian regulation, suggesting separate roles in photosynthesis-associated and other respiratory NADH oxidation. Genes from all three gene families encode proteins exclusively targeted to mitochondria, as revealed by expression of green fluorescent fusion proteins and by western blotting of fractionated cells. Phylogenetic analysis indicates that ndc1 affiliates with cyanobacterial type II NADH dehydrogenase genes, suggesting that this gene entered the eukaryotic cell via the chloroplast progenitor. The ndc1 should then have been transferred to the nucleus and acquired a signal for mitochondrial targeting of the protein product. Although they are of different origin, the nda, ndb, and ndc genes carry an identical intron position.
  •  
40.
  • Moparthi, Lavanya, et al. (author)
  • Electrophile-Induced Conformational Switch of the Human TRPA1 Ion Channel Detected by Mass Spectrometry
  • 2020
  • In: International Journal of Molecular Sciences. - : MDPI. - 1661-6596 .- 1422-0067. ; 21:18
  • Journal article (peer-reviewed)abstract
    • The human Transient Receptor Potential A1 (hTRPA1) ion channel, also known as the wasabi receptor, acts as a biosensor of various potentially harmful stimuli. It is activated by a wide range of chemicals, including the electrophilic compound N-methylmaleimide (NMM), but the mechanism of activation is not fully understood. Here, we used mass spectrometry to map and quantify the covalent labeling in hTRPA1 at three different concentrations of NMM. A functional truncated version of hTRPA1 (Delta 1-688 hTRPA1), lacking the large N-terminal ankyrin repeat domain (ARD), was also assessed in the same way. In the full length hTRPA1, the labeling of different cysteines ranged from nil up to 95% already at the lowest concentration of NMM, suggesting large differences in reactivity of the thiols. Most important, the labeling of some cysteine residues increased while others decreased with the concentration of NMM, both in the full length and the truncated protein. These findings indicate a conformational switch of the proteins, possibly associated with activation or desensitization of the ion channel. In addition, several lysines in the transmembrane domain and the proximal N-terminal region were labeled by NMM, raising the possibility that lysines are also key targets for electrophilic activation of hTRPA1.
  •  
41.
  • Moparthi, Lavanya, et al. (author)
  • Human TRPA1 is a heat sensor displaying intrinsic U-shaped thermosensitivity
  • 2016
  • In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
  • Journal article (peer-reviewed)abstract
    • Thermosensitive Transient Receptor Potential (TRP) channels are believed to respond to either cold or heat. In the case of TRP subtype A1 (TRPA1), there seems to be a species-dependent divergence in temperature sensation as non-mammalian TRPA1 is heat-sensitive whereas mammalian TRPA1 is sensitive to cold. It has been speculated but never experimentally proven that TRPA1 and other temperature-sensitive ion channels have the inherent capability of responding to both cold and heat. Here we show that redox modification and ligands affect human TRPA1 (hTRPA1) cold and heat sensing properties in lipid bilayer and whole-cell patch-clamp recordings as well as heat-evoked TRPA1-dependent calcitonin gene-related peptide (CGRP) release from mouse trachea. Studies of purified hTRPA1 intrinsic tryptophan fluorescence, in the absence of lipid bilayer, consolidate hTRPA1 as an intrinsic bidirectional thermosensor that is modified by the redox state and ligands. Thus, the heat sensing property of TRPA1 is conserved in mammalians, in which TRPA1 may contribute to sensing warmth and uncomfortable heat in addition to noxious cold.
  •  
42.
  • Moparthi, Lavanya, et al. (author)
  • Human TRPA1 is intrinsically cold- and chemosensitive with and without its N-terminal ankyrin repeat domain.
  • 2014
  • In: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 111:47, s. 16901-16906
  • Journal article (peer-reviewed)abstract
    • We have purified and reconstituted human transient receptor potential (TRP) subtype A1 (hTRPA1) into lipid bilayers and recorded single-channel currents to understand its inherent thermo- and chemosensory properties as well as the role of the ankyrin repeat domain (ARD) of the N terminus in channel behavior. We report that hTRPA1 with and without its N-terminal ARD (Δ1-688 hTRPA1) is intrinsically cold-sensitive, and thus, cold-sensing properties of hTRPA1 reside outside the N-terminal ARD. We show activation of hTRPA1 by the thiol oxidant 2-((biotinoyl)amino)ethyl methanethiosulfonate (MTSEA-biotin) and that electrophilic compounds activate hTRPA1 in the presence and absence of the N-terminal ARD. The nonelectrophilic compounds menthol and the cannabinoid Δ(9)-tetrahydrocannabiorcol (C16) directly activate hTRPA1 at different sites independent of the N-terminal ARD. The TRPA1 antagonist HC030031 inhibited cold and chemical activation of hTRPA1 and Δ1-688 hTRPA1, supporting a direct interaction with hTRPA1 outside the N-terminal ARD. These findings show that hTRPA1 is an intrinsically cold- and chemosensitive ion channel. Thus, second messengers, including Ca(2+), or accessory proteins are not needed for hTRPA1 responses to cold or chemical activators. We suggest that conformational changes outside the N-terminal ARD by cold, electrophiles, and nonelectrophiles are important in hTRPA1 channel gating and that targeting chemical interaction sites outside the N-terminal ARD provides possibilities to fine tune TRPA1-based drug therapies (e.g., for treatment of pain associated with cold hypersensitivity and cardiovascular disease).
  •  
43.
  • Nordén, Kristina, et al. (author)
  • Increasing gene dosage greatly enhances recombinant expression of aquaporins in Pichia pastoris
  • 2011
  • In: BMC Biotechnology. - : Springer Science and Business Media LLC. - 1472-6750. ; 11
  • Journal article (peer-reviewed)abstract
    • Background: When performing functional and structural studies, large quantities of pure protein are desired. Most membrane proteins are however not abundantly expressed in their native tissues, which in general rules out purification from natural sources. Heterologous expression, especially of eukaryotic membrane proteins, has also proven to be challenging. The development of expression systems in insect cells and yeasts has resulted in an increase in successful overexpression of eukaryotic proteins. High yields of membrane protein from such hosts are however not guaranteed and several, to a large extent unexplored, factors may influence recombinant expression levels. In this report we have used four isoforms of aquaporins to systematically investigate parameters that may affect protein yield when overexpressing membrane proteins in the yeast Pichia pastoris. Results: By comparing clones carrying a single gene copy, we show a remarkable variation in recombinant protein expression between isoforms and that the poor expression observed for one of the isoforms could only in part be explained by reduced transcript levels. Furthermore, we show that heterologous expression levels of all four aquaporin isoforms strongly respond to an increase in recombinant gene dosage, independent of the amount of protein expressed from a single gene copy. We also demonstrate that the increased expression does not appear to compromise the protein folding and the membrane localisation. Conclusions: We report a convenient and robust method based on qPCR to determine recombinant gene dosage. The method is generic for all constructs based on the pPICZ vectors and offers an inexpensive, quick and reliable means of characterising recombinant P. pastoris clones. By using this method we show that: (1) heterologous expression of all aquaporins investigated respond strongly to an increase in recombinant gene dosage (2) expression from a single recombinant gene copy varies in an isoform dependent manner (3) the poor expression observed for AtSIP1;1 is mainly caused by posttranscriptional limitations. The protein folding and membrane localisation seems to be unaffected by increased expression levels. Thus a screen for elevated gene dosage can routinely be performed for identification of P. pastoris clones with high expression levels of aquaporins and other classes of membrane proteins.
  •  
44.
  • Ohlsson, Gabriel, 1982, et al. (author)
  • Solute transport on the sub 100 ms scale across the lipid bilayer membrane of individual proteoliposomes
  • 2012
  • In: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 12:22, s. 4635-4643
  • Journal article (peer-reviewed)abstract
    • Screening assays designed to probe ligand and drug-candidate regulation of membrane proteins responsible for ion-translocation across the cell membrane are wide spread, while efficient means to screen membrane-protein facilitated transport of uncharged solutes are sparse. We report on a microfluidic-based system to monitor transport of uncharged solutes across the membrane of multiple (>100) individually resolved surface-immobilized liposomes. This was accomplished by rapidly switching (<10 ms) the solution above dye-containing liposomes immobilized on the floor of a microfluidic channel. With liposomes encapsulating the pH-sensitive dye carboxyfluorescein (CF), internal changes in pH induced by transport of a weak acid (acetic acid) could be measured at time scales down to 25 ms. The applicability of the set up to study biological transport reactions was demonstrated by examining the osmotic water permeability of human aquaporin (AQP5) reconstituted in proteoliposomes. In this case, the rate of osmotic-induced volume changes of individual proteoliposomes was time resolved by imaging the self quenching of encapsulated calcein in response to an osmotic gradient. Single-liposome analysis of both pure and AQP5-containing liposomes revealed a relatively large heterogeneity in osmotic permeability. Still, in the case of AQP5-containing liposomes, the single liposome data suggest that the membrane-protein incorporation efficiency depends on liposome size, with higher incorporation efficiency for larger liposomes. The benefit of low sample consumption and automated liquid handling is discussed in terms of pharmaceutical screening applications.
  •  
45.
  • Plasencia, Ines, et al. (author)
  • Structure and Stability of the Spinach Aquaporin SoPIP2;1 in Detergent Micelles and Lipid Membranes
  • 2011
  • In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:2
  • Journal article (peer-reviewed)abstract
    • Background: SoPIP2;1 constitutes one of the major integral proteins in spinach leaf plasma membranes and belongs to the aquaporin family. SoPIP2;1 is a highly permeable and selective water channel that has been successfully overexpressed and purified with high yields. In order to optimize reconstitution of the purified protein into biomimetic systems, we have here for the first time characterized the structural stability of SoPIP2;1. Methodology/Principal Finding: We have characterized the protein structural stability after purification and after reconstitution into detergent micelles and proteoliposomes using circular dichroism and fluorescence spectroscopy techniques. The structure of SoPIP2;1 was analyzed either with the protein solubilized with octyl-beta-D-glucopyranoside (OG) or reconstituted into lipid membranes formed by E. coli lipids, diphytanoylphosphatidylcholine (DPhPC), or reconstituted into lipid membranes formed from mixtures of 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPE), 1-palmitoyl-2-oleoyl-phosphatidylethanolamine (POPE), 1-palmitoyl-2-oleoyl-phosphatidylserine (POPS), and ergosterol. Generally, SoPIP2;1 secondary structure was found to be predominantly a-helical in accordance with crystallographic data. The protein has a high thermal structural stability in detergent solutions, with an irreversible thermal unfolding occurring at a melting temperature of 58 degrees C. Incorporation of the protein into lipid membranes increases the structural stability as evidenced by an increased melting temperature of up to 70 degrees C. Conclusion/Significance: The results of this study provide insights into SoPIP2;1 stability in various host membranes and suggest suitable choices of detergent and lipid composition for reconstitution of SoPIP2;1 into biomimetic membranes for biotechnological applications.
  •  
46.
  • Schussler, Manuela Desiree, et al. (author)
  • The effects of the loss of TIP1;1 and TIP1;2 aquaporins in Arabidopsis thaliana
  • 2008
  • In: Plant Journal. - 1365-313X. ; 56:5, s. 756-767
  • Journal article (peer-reviewed)abstract
    • Loss of aquaporin TIP1;1 in Arabidopsis has been suggested to result in early senescence and plant death. This was based on the fact that a partial reduction of TIP1;1 by RNA interference (RNAi) led to gradual phenotypes, ranging from indistinguishable from wild type to lethality, depending on the degree of downregulation of the target messenger, and displaying pleiotropic effects in primary metabolism and cell signalling. A hypothesis was put forward to suggest that TIP1;1, apart from its transport function, may play an essential role in vesicle routing. Here we identify an Arabidopsis transposon insertion line tip1;1-1 that is completely devoid of TIP1;1 protein, as demonstrated by western blotting and immunolocalization using an isoform-specific antibody. Strikingly, the complete absence of the protein did not result in any significant effect on metabolism or elemental composition of the plants. Microarray analysis did not indicate increased expression of other aquaporins to compensate for the lack of TIP1;1 in tip1;1-1. We further developed a double mutant of TIPs in Arabidopsis, lacking both TIP1;1 and its closest paralog TIP1;2. Arabidopsis mutants lacking both TIP1;1 and TIP1;2 showed a minor increase in anthocyanin content, and a reduction in catalase activity, but showed no changes in water status. In contrast to earlier reports, plants lacking TIP1;1 and TIP1;2 aquaporins are alive and thriving. We suggest that RNAi directed towards TIP1;1 may have resulted in off-target gene silencing, a notion that is potentially interesting for various studies analysing gene function by RNAi.
  •  
47.
  • Sjövall Larsen, Sara, et al. (author)
  • Purification and characterization of two protein kinases acting on the aquaporin SoPIP2; 1
  • 2006
  • In: Biochimica et Biophysica Acta - Biomembranes. - : Elsevier BV. - 0005-2736. ; 1758:8, s. 1157-1164
  • Journal article (peer-reviewed)abstract
    • Aquaporins are water channel proteins that facilitate the movement of water and other small solutes across biological membranes. Plants usually have large aquaporin families, providing them with many ways to regulate the water transport. Some aquaporins are regulated post-translationally by phosphorylation. We have previously shown that the water channel activity of SoP1P2;1, an aquaporin in the plasma membrane of spinach leaves, was enhanced by phosphorylation at Ser115 and Ser274. These two serine residues are highly conserved in all plasma membrane aquaporins of the PIP2 subgroup. In this study we have purified and characterized two protein kinases phosphorylating Ser115 and Ser274 in SoPIP2;1. By anion exchange chromatography, the Ser115 kinase was purified from the soluble protein fraction isolated from spinach leaves. The Ca2+-dependent Ser274 kinase was purified by peptide affinity chromatography using plasma membranes isolated from spinach leaves. When characterized, the Ser115 kinase was Mg2+-dependent, Ca2+-independent and had a pH-optimum at 6.5. In accordance with previous studies using the oocyte expression system, site-directed mutagenesis and kinase and phosphatase inhibitors, the phosphorylation of Ser274, but not of Ser115, was increased in the presence of phosphatase inhibitors while kinase inhibitors decreased the phosphorylation of both Ser274 and Ser115. The molecular weight of the Ser274 kinase was approximately 50 kDa. The identification and characterization of these two protein kinases is an important step towards elucidating the signal transduction pathway for gating of the aquaporin SoPIP2;1.
  •  
48.
  • Sonntag, Yonathan, et al. (author)
  • Identification and characterization of potent and selective aquaporin-3 and aquaporin-7 inhibitors
  • 2019
  • In: Journal of Biological Chemistry. - 1083-351X. ; 294:18, s. 7377-7387
  • Journal article (peer-reviewed)abstract
    • The aquaglyceroporins are a subfamily of aquaporins that conduct both water and glycerol. Aquaporin-3 (AQP3) has an important physiological function in renal water reabsorption, and AQP3-mediated hydrogen peroxide (H2O2) permeability can enhance cytokine signaling in several cell types. The related aquaglyceroporin AQP7 is required for dendritic cell chemokine responses and antigen uptake. Selective small-molecule inhibitors are desirable tools for investigating the biological and pathological roles of these and other AQP isoforms. Here, using a calcein fluorescence quenching assay we screened a library of 7360 drug-like small molecules for inhibition of mouse AQP3 water permeability. Hit confirmation and expansion with commercially available substances identified the ortho-chloride-containing compound DFP00173, which inhibited mouse and human AQP3 with an IC50 of ~0.1-0.4 μM but had low efficacy toward mouse AQPs 7 and 9. Surprisingly, inhibitor specificity testing revealed that the methylurea-linked compound Z433927330, a partial AQP3 inhibitor (IC50 ~0.7-0.9 μM), is a potent and efficacious inhibitor of mouse AQP7 water permeability (IC50 ~0.2 μM). Stopped-flow light-scattering measurements confirmed that DFP00173 and Z433927330 inhibit AQP3 glycerol permeability in human erythrocytes. Moreover, DFP00173, Z433927330, and the previously identified AQP9 inhibitor RF03176 blocked aquaglyceroporin H2O2 permeability. Molecular docking to AQP3, AQP7, and AQP9 homology models suggested interactions between these inhibitors and aquaglyceroporins at similar binding sites. DFP00173 and Z433927330 constitute selective and potent AQP3 and AQP7 inhibitors, respectively, and contribute to a set of isoform-specific aquaglyceroporin inhibitors that will facilitate the evaluation of these AQP isoforms as drug targets.
  •  
49.
  • Strandberg, Helin, et al. (author)
  • Structural Basis for the Interaction between the Ezrin FERM-Domain and Human Aquaporins
  • 2024
  • In: International Journal of Molecular Sciences. - 1422-0067. ; 25:14
  • Journal article (peer-reviewed)abstract
    • The Ezrin/Radixin/Moesin (ERM) family of proteins act as cross-linkers between the plasma membrane and the actin cytoskeleton. This mechanism plays an essential role in processes related to membrane remodeling and organization, such as cell polarization, morphogenesis and adhesion, as well as in membrane protein trafficking and signaling pathways. For several human aquaporin (AQP) isoforms, an interaction between the ezrin band Four-point-one, Ezrin, Radixin, Moesin (FERM)-domain and the AQP C-terminus has been demonstrated, and this is believed to be important for AQP localization in the plasma membrane. Here, we investigate the structural basis for the interaction between ezrin and two human AQPs: AQP2 and AQP5. Using microscale thermophoresis, we show that full-length AQP2 and AQP5 as well as peptides corresponding to their C-termini interact with the ezrin FERM-domain with affinities in the low micromolar range. Modelling of the AQP2 and AQP5 FERM complexes using ColabFold reveals a common mode of binding in which the proximal and distal parts of the AQP C-termini bind simultaneously to distinct binding sites of FERM. While the interaction at each site closely resembles other FERM-complexes, the concurrent interaction with both sites has only been observed in the complex between moesin and its C-terminus which causes auto-inhibition. The proposed interaction between AQP2/AQP5 and FERM thus represents a novel binding mode for extrinsic ERM-interacting partners.
  •  
50.
  • Strandberg, Jonas, 1983- (author)
  • Taking a Bite out of Diversity - Taxonomy and systematics of biting midges
  • 2016
  • Doctoral thesis (other academic/artistic)abstract
    • The biting midges (family Ceratopogonidae) is one of the most species rich amongst the biting flies (Diptera) and has been recorded from most parts of the world. The species are mostly known for their capability to act as vectors for several important diseases, which have helped in shaping the focus to one of its genera, Culicoides Latreille, 1809. This thesis gives an overview of the knowledge of the Swedish diversity, in the first paper (paper I) with a closer look at the species of Dasyhelea Kieffer, 1911 where all twenty species found in Sweden are presented with their associated localities, and two new species are described.  In the second paper (paper II) the biting midge diversity of Sweden is presented based on specimens collected from several localities. All these individuals were barcoded using the mitochondrial cytochrome oxidase I gene (COI). The analysis included 773 specimens that were assigned into 214 barcoding clusters (BINs) and sorted into 164 groups based on their morphology. The third paper (paper III) broadens the scale were the evolutionary relationships within the family are investigated by applying five protein coding genes (COI, CAD, TPI, AATS and PGD) and specimens from different parts of the World. The analysis recovers Ceratopogonini, Forcipomyia Meigen, 1818 and Bezzia Kieffer, 1899 as paraphyletic and Palpomyia Meigen, 1818 polyphyletic. In the last and fourth paper (paper IV) the family is used as a model organism together with Hymenoptera for an alternative analysis method for reducing the impact of saturation and long-branch attraction using non-synonymous coding (e.g. Degen1) on only parts of a dataset. The effectiveness of the method is compared to the removal of the faster evolving third codon position. The result yields a higher number of supported nodes as well as a higher median of support for the method as well as an ability to reduce long-branch attraction artifacts.
  •  
Skapa referenser, mejla, bekava och länka
  • Result 1-50 of 56
Type of publication
journal article (49)
research review (3)
other publication (2)
doctoral thesis (2)
Type of content
peer-reviewed (52)
other academic/artistic (4)
Author/Editor
Johanson, Urban (53)
Kjellbom, Per (30)
Nordén, Kristina (6)
Karlsson, Maria (6)
Danielson, Jonas (5)
Alexandersson, Erik (5)
show more...
Agemark, Maria (5)
Sonntag, Yonathan (5)
Engström, Peter (4)
Gustavsson, Sofia (4)
Hughes, Diarmaid, 19 ... (3)
Tandre, Karolina (3)
Sjövall Larsen, Sara (3)
Englund, Marie (3)
Ehrenberg, Måns (2)
Löfstedt, Christer (2)
Larsson, Christer (2)
Kjellström, Sven (2)
Ampah-Korsah, Henry (2)
Fraysse, Laure (2)
Englund, M. (1)
Singh, Birendra (1)
Riesbeck, Kristian (1)
Wang, Yi (1)
Kowal, Julia (1)
Kukulski, Wanda (1)
Gustavsson, Niklas (1)
Engel, Andreas (1)
Agius, Stephanie C (1)
Rasmusson, Allan (1)
Höök, Fredrik, 1966 (1)
Nielsen, Soren (1)
Tajkhorshid, Emad (1)
Grosse-Wilde, Ewald (1)
Tegenfeldt, Jonas O. (1)
Sundström, Jens (1)
Beech, Jason (1)
Braun, T. (1)
Gourdon, Pontus (1)
Törnroth-Horsefield, ... (1)
Kvarnheden, A. (1)
Zygmunt, Peter (1)
Högestätt, Edward (1)
Råde, Johan (1)
Moparthi, Vamsi (1)
Fontes, Magnus (1)
Fotiadis, D (1)
Carlquist, Magnus (1)
Olsson, Robin (1)
Artner, Isabella (1)
show less...
University
Lund University (50)
Uppsala University (9)
Chalmers University of Technology (5)
University of Gothenburg (4)
Umeå University (2)
Stockholm University (1)
show more...
Linköping University (1)
show less...
Language
English (53)
Undefined language (3)
Research subject (UKÄ/SCB)
Natural sciences (45)
Medical and Health Sciences (8)
Engineering and Technology (2)
Social Sciences (1)

Year

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Close

Copy and save the link in order to return to this view