| 11. |
- Gustafsson, Robert, et al.
(författare)
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Structure and Characterization of Phosphoglucomutase 5 from Atlantic and Baltic Herring : An Inactive Enzyme with Intact Substrate Binding
- 2020
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Ingår i: Biomolecules. - : MDPI AG. - 2218-273X. ; 10:12
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Tidskriftsartikel (refereegranskat)abstract
- Phosphoglucomutase 5 (PGM5) in humans is known as a structural muscle protein without enzymatic activity, but detailed understanding of its function is lacking. PGM5 belongs to the alpha-D-phosphohexomutase family and is closely related to the enzymatically active metabolic enzyme PGM1. In the Atlantic herring, Clupea harengus, PGM5 is one of the genes strongly associated with ecological adaptation to the brackish Baltic Sea. We here present the first crystal structures of PGM5, from the Atlantic and Baltic herring, diering by a single substitution Ala330Val. The structure of PGM5 is overall highly similar to structures of PGM1. The structure of the Baltic herring PGM5 in complex with the substrate glucose-1-phosphate shows conserved substrate binding and active site compared to human PGM1, but both PGM5 variants lack phosphoglucomutase activity under the tested conditions. Structure comparison and sequence analysis of PGM5 and PGM1 from fish and mammals suggest that the lacking enzymatic activity of PGM5 is related to dierences in active-site loops that are important for flipping of the reaction intermediate. The Ala330Val substitution does not alter structure or biophysical properties of PGM5 but, due to its surface-exposed location, could affect interactions with protein-binding partners.
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| 12. |
- Simon, Philipp S., et al.
(författare)
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Capturing the sequence of events during the water oxidation reaction in photosynthesis using XFELs
- 2023
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Ingår i: FEBS Letters. - : John Wiley & Sons. - 0014-5793 .- 1873-3468. ; 597:1, s. 30-37
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Tidskriftsartikel (refereegranskat)abstract
- Ever since the discovery that Mn was required for oxygen evolution in plants by Pirson in 1937 and the period-four oscillation in flash-induced oxygen evolution by Joliot and Kok in the 1970s, understanding of this process has advanced enormously using state-of-the-art methods. The most recent in this series of innovative techniques was the introduction of X-ray free-electron lasers (XFELs) a decade ago, which led to another quantum leap in the understanding in this field, by enabling operando X-ray structural and X-ray spectroscopy studies at room temperature. This review summarizes the current understanding of the structure of Photosystem II (PS II) and its catalytic centre, the Mn4CaO5 complex, in the intermediate Si (i = 0–4)-states of the Kok cycle, obtained using XFELs.
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| 13. |
- Fröhlich, Christopher, et al.
(författare)
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Structural and biochemical characterization of the environmental MBLs MYO-1, ECV-1 and SHD-1.
- 2020
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Ingår i: The Journal of antimicrobial chemotherapy. - : Oxford University Press (OUP). - 1460-2091 .- 0305-7453. ; 75:9, s. 2554-2563
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Tidskriftsartikel (refereegranskat)abstract
- MBLs form a large and heterogeneous group of bacterial enzymes conferring resistance to β-lactam antibiotics, including carbapenems. A large environmental reservoir of MBLs has been identified, which can act as a source for transfer into human pathogens. Therefore, structural investigation of environmental and clinically rare MBLs can give new insights into structure-activity relationships to explore the role of catalytic and second shell residues, which are under selective pressure.To investigate the structure and activity of the environmental subclass B1 MBLs MYO-1, SHD-1 and ECV-1.The respective genes of these MBLs were cloned into vectors and expressed in Escherichia coli. Purified enzymes were characterized with respect to their catalytic efficiency (kcat/Km). The enzymatic activities and MICs were determined for a panel of different β-lactams, including penicillins, cephalosporins and carbapenems. Thermostability was measured and structures were solved using X-ray crystallography (MYO-1 and ECV-1) or generated by homology modelling (SHD-1).Expression of the environmental MBLs in E. coli resulted in the characteristic MBL profile, not affecting aztreonam susceptibility and decreasing susceptibility to carbapenems, cephalosporins and penicillins. The purified enzymes showed variable catalytic activity in the order of <5% to ∼70% compared with the clinically widespread NDM-1. The thermostability of ECV-1 and SHD-1 was up to 8°C higher than that of MYO-1 and NDM-1. Using solved structures and molecular modelling, we identified differences in their second shell composition, possibly responsible for their relatively low hydrolytic activity.These results show the importance of environmental species acting as reservoirs for MBL-encoding genes.
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| 14. |
- Kang, Wenjing, 1988-
(författare)
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microRNAs: from biogenesis to organismal tracing
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- MicroRNAs (miRNAs) are short noncoding RNAs of around 22 nucleotides in length, which help to shape the expression of most mRNAs. Perturbation of miRNA expression has revealed a variety of defects in development, cell specification, physiology and behavior. This thesis focuses on two topics of miRNA: identification of structural features that influence miRNA biogenesis (Paper I) and application of taxonomical marker miRNAs to resolve organismal origin of samples (Paper II and III).The current model of miRNA hairpin biogenesis has limited information content and appears to be incomplete. In paper I, we apply a novel high-throughput screening method to profile the optimal structure of miRNA hairpins for efficient and precise miRNA biogenesis. The optimal structure consists of tight and loose local structures across the hairpin, which reflects the constraints of biogenesis proteins. We find that miRNA hairpins with stable lower basal stem are more efficiently processed and have a higher expression level in tissues of 20 animal species. We address that the structural features - which have been largely neglected in the current model - are in fact as important as the well-known sequence motifs.New miRNAs are continuously added over evolutionary time and are rarely secondarily lost, making them ideal taxonomical markers. In paper II, we demonstrate as a proof-of-principle that miRNAs can be used to trace biological sample back to the lineage or even species of origin. Based on the marker miRNAs, we develop miRTrace, the first software to accurately trace miRNA sequences back to their taxonomical origin. The method can sensitively identify the origin of single cells and detect parasitic nematode RNA in mammalian host blood sample. In paper III, we apply miRNA tracing to address a controversial question about the origin of the exogenous plant miRNAs (xenomiRs) found in human samples, and which have been proposed to regulate human gene expression. Our computational and experimental results provide evidence that xenomiRs are derived from technical artifacts rather than dietary intake.
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| 15. |
- Diamanti, Riccardo, et al.
(författare)
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Comparative structural analysis provides new insights into the function of R2-like ligand-binding oxidase
- 2022
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Ingår i: FEBS Letters. - : John Wiley & Sons. - 0014-5793 .- 1873-3468. ; 596:12, s. 1600-1610
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Tidskriftsartikel (refereegranskat)abstract
- R2-like ligand-binding oxidase (R2lox) is a ferritin-like protein that harbours a heterodinuclear manganese–iron active site. Although R2lox function is yet to be established, the enzyme binds a fatty acid ligand coordinating the metal centre and catalyses the formation of a tyrosine–valine ether cross-link in the protein scaffold upon O2 activation. Here, we characterized the ligands copurified with R2lox by mass spectrometry-based metabolomics. Moreover, we present the crystal structures of two new homologs of R2lox, from Saccharopolyspora erythraea and Sulfolobus acidocaldarius, at 1.38 Å and 2.26 Å resolution, respectively, providing the highest resolution structure for R2lox, as well as new insights into putative mechanisms regulating the function of the enzyme.
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| 16. |
- Ezzedine, Jade A., et al.
(författare)
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Adaptive traits of cysts of the snow alga Sanguina nivaloides unveiled by 3D subcellular imaging
- 2023
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Ingår i: Nature Communications. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Sanguina nivaloides is the main alga forming red snowfields in high mountains and Polar Regions. It is non-cultivable. Analysis of environmental samples by X-ray tomography, focused-ion-beam scanning-electron-microscopy, physicochemical and physiological characterization reveal adaptive traits accounting for algal capacity to reside in snow. Cysts populate liquid water at the periphery of ice, are photosynthetically active, can survive for months, and are sensitive to freezing. They harbor a wrinkled plasma membrane expanding the interface with environment. Ionomic analysis supports a cell efflux of K+, and assimilation of phosphorus. Glycerolipidomic analysis confirms a phosphate limitation. The chloroplast contains thylakoids oriented in all directions, fixes carbon in a central pyrenoid and produces starch in peripheral protuberances. Analysis of cells kept in the dark shows that starch is a short-term carbon storage. The biogenesis of cytosolic droplets shows that they are loaded with triacylglycerol and carotenoids for long-term carbon storage and protection against oxidative stress.
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| 17. |
- Grāve, Kristīne, et al.
(författare)
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The Bacillus anthracis class Ib ribonucleotide reductase subunit NrdF intrinsically selects manganese over iron
- 2020
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Ingår i: Journal of Biological Inorganic Chemistry. - : Springer Science and Business Media LLC. - 0949-8257 .- 1432-1327. ; 25:4, s. 571-582
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Tidskriftsartikel (refereegranskat)abstract
- Correct protein metallation in the complex mixture of the cell is a prerequisite for metalloprotein function. While some metals, such as Cu, are commonly chaperoned, specificity towards metals earlier in the Irving-Williams series is achieved through other means, the determinants of which are poorly understood. The dimetal carboxylate family of proteins provides an intriguing example, as different proteins, while sharing a common fold and the same 4-carboxylate 2-histidine coordination sphere, are known to require either a Fe/Fe, Mn/Fe or Mn/Mn cofactor for function. We previously showed that the R2lox proteins from this family spontaneously assemble the heterodinuclear Mn/Fe cofactor. Here we show that the class Ib ribonucleotide reductase R2 protein from Bacillus anthracis spontaneously assembles a Mn/Mn cofactor in vitro, under both aerobic and anoxic conditions, when the metal-free protein is subjected to incubation with Mn-II and Fe-II in equal concentrations. This observation provides an example of a protein scaffold intrinsically predisposed to defy the Irving-Williams series and supports the assumption that the Mn/Mn cofactor is the biologically relevant cofactor in vivo. Substitution of a second coordination sphere residue changes the spontaneous metallation of the protein to predominantly form a heterodinuclear Mn/Fe cofactor under aerobic conditions and a Mn/Mn metal center under anoxic conditions. Together, the results describe the intrinsic metal specificity of class Ib RNR and provide insight into control mechanisms for protein metallation.
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| 18. |
- Kosek, David M, et al.
(författare)
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Efficient 3′-pairing renders microRNA targeting less sensitive to mRNA seed accessibility
- 2023
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Ingår i: Nucleic Acids Research. - : Oxford University Press. - 0305-1048 .- 1362-4962. ; 51:20, s. 11162-11177
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Tidskriftsartikel (refereegranskat)abstract
- MicroRNAs (miRNAs) are short RNAs that post-transcriptionally regulate gene expression by binding to specific sites in mRNAs. Site recognition is primarily mediated by the seed region (nucleotides g2–g8 in the miRNA), but pairing beyond the seed (3′-pairing) is important for some miRNA:target interactions. Here, we use SHAPE, luciferase reporter assays and transcriptomics analyses to study the combined effect of 3′-pairing and secondary structures in mRNAs on repression efficiency. Using the interaction between miR-34a and its SIRT1 binding site as a model, we provide structural and functional evidence that 3′-pairing can compensate for low seed-binding site accessibility, enabling repression of sites that would otherwise be ineffective. We show that miRNA 3′-pairing regions can productively base-pair with nucleotides far upstream of the seed-binding site and that both hairpins and unstructured bulges within the target site are tolerated. We use SHAPE to show that sequences that overcome inaccessible seed-binding sites by strong 3′-pairing adopt the predicted structures and corroborate the model using luciferase assays and high-throughput modelling of 8177 3′-UTR targets for six miRNAs. Finally, we demonstrate that PHB2, a target of miR-141, is an inaccessible target rescued by efficient 3′-pairing. We propose that these results could refine predictions of effective target sites.
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| 19. |
- Manzetti, Sergio, 1975-
(författare)
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Computational Ecotoxicology
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Human society has progressed by polluting ecosystems since at least the early industrial revolution. Large amounts of harmful chemical compounds have been dispersed in soils, seas, ground waters and wildlife habitats by industrial and anthropomorphic activities over the last two centuries, leading to a persistent toxicological load on the environment. Pollution is a threat to biodiversity, to the health of ecosystems, and to all living organisms. Advances in environmental sciences are needed so that pollutants can be distinguished from harmless compounds. New methods could ease the enormous task of sorting out hazardous chemicals, and also facilitate the study of existing problems in ecotoxicology, which are often hampered by insufficient data. In our research, we apply the methods of computational chemistry to predict the interactions of various toxins, carcinogens, nanoparticles and xenobiotics with proteins, DNA, and cell membranes. Methods such as molecular dynamics simulations, docking, and quantum chemistry are at the core of these studies, each having its role in facilitating the enormous task of transforming in vitro ecotoxicology to in silico ecotoxicology. We perform detailed studies of a few compounds and receptors, as well as larger, more comprehensive groups of compounds. We also outline approaches for drawing computational conclusions about the molecular behaviour of various potential environmental toxins by modelling their interactions with DNA and proteins, and we use partition coefficients to describe their ability to permeate the cell membrane. Methods for studying the purification of pollutants from essential sources, such as water, are proposed. We also investigate the emerging problem of nanoparticle pollution and propose computational approaches to model the formation of nanoparticles from combustion emissions and the interactions of such particles with atmospheric components.
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| 20. |
- Munke, Anna, et al.
(författare)
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Primordial Capsid and Spooled ssDNA Genome Structures Unravel Ancestral Events of Eukaryotic Viruses
- 2022
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Ingår i: mBio. - : American Society for Microbiology. - 2161-2129 .- 2150-7511. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- Marine algae viruses are important for controlling microorganism communities in the marine ecosystem and played fundamental roles during the early events of viral evolution. Here, we have focused on one major group of marine algae viruses, the single-stranded DNA (ssDNA) viruses from the Bacilladnaviridae family. We present the capsid structure of the bacilladnavirus Chaetoceros tenuissimus DNA virus type II (CtenDNAV-II), determined at 2.4-Å resolution. A structure-based phylogenetic analysis supported the previous theory that bacilladnaviruses have acquired their capsid protein via horizontal gene transfer from a ssRNA virus. The capsid protein contains the widespread virus jelly-roll fold but has additional unique features; a third β-sheet and a long C-terminal tail. Furthermore, a low-resolution reconstruction of the CtenDNAV-II genome revealed a partially spooled structure, an arrangement previously only described for dsRNA and dsDNA viruses. Together, these results exemplify the importance of genetic recombination for the emergence and evolution of ssDNA viruses and provide important insights into the underlying mechanisms that dictate genome organization.IMPORTANCE Single-stranded DNA (ssDNA) viruses are an extremely widespread group of viruses that infect diverse hosts from all three domains of life, consequently having great economic, medical, and ecological importance. In particular, bacilladnaviruses are highly abundant in marine sediments and greatly influence the dynamic appearance and disappearance of certain algae species. Despite the importance of ssDNA viruses and the last couple of years' advancements in cryo-electron microscopy, structural information on the genomes of ssDNA viruses remains limited. This paper describes two important achievements: (i) the first atomic structure of a bacilladnavirus capsid, which revealed that the capsid protein gene presumably was acquired from a ssRNA virus in early evolutionary events; and (ii) the structural organization of a ssDNA genome, which retains a spooled arrangement that previously only been observed for double-stranded viruses.
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