| 1. |
- Bakali, Amin, et al.
(författare)
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Crystal structure of YegS, a homologue to the mammalian diacylglycerol kinases, reveals a novel regulatory metal binding site
- 2007
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 282:27, s. 19644-19652
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Tidskriftsartikel (refereegranskat)abstract
- The human lipid kinase family controls cell proliferation, differentiation, and tumorigenesis and includes diacylglycerol kinases, sphingosine kinases, and ceramide kinases. YegS is an Escherichia coli protein with significant sequence homology to the catalytic domain of the human lipid kinases. We have solved the crystal structure of YegS and shown that it is a lipid kinase with phosphatidylglycerol kinase activity. The crystal structure reveals a two-domain protein with significant structural similarity to a family of NAD kinases. The active site is located in the interdomain cleft formed by four conserved sequence motifs. Surprisingly, the structure reveals a novel metal binding site composed of residues conserved in most lipid kinases.
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| 2. |
- Bhushan, Shashi, et al.
(författare)
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Proteolytic mechanism of a novel mitochondrial and chloroplastic PreP peptidasome.
- 2006
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Ingår i: Biol Chem. - 1431-6730. ; 387:8, s. 1087-90
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Tidskriftsartikel (refereegranskat)abstract
- The 2.1-A-resolution crystal structure of the novel mitochondrial and chloroplastic metalloendopeptidase, AtPreP1, revealed a unique peptidasome structure, in which the two halves of the enzyme completely enfold a huge proteolytic cavity. Based on the structure, we proposed a novel mechanism for proteolysis involving hinge-bending motions, which cause the protease to open and close in response to substrate binding. We generated four double-mutants of AtPreP1 by introducing cysteines at positions where disulfide bonds can be formed in order to lock and unlock the protease and tested the activity under oxidizing and reducing conditions. The overall results support the proposed mechanism.
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| 3. |
- Falkevall, Annelie, et al.
(författare)
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Degradation of the amyloid beta-protein by the novel mitochondrial peptidasome, PreP
- 2006
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 281:39, s. 29096-29104
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Tidskriftsartikel (refereegranskat)abstract
- Recently we have identified the novel mitochondrial peptidase responsible for degrading presequences and other short unstructured peptides in mitochondria, the presequence peptidase, which we named PreP peptidasome. In the present study we have identified and characterized the human PreP homologue, hPreP, in brain mitochondria, and we show its capacity to degrade the amyloid beta-protein (Abeta). PreP belongs to the pitrilysin oligopeptidase family M16C containing an inverted zinc-binding motif. We show that hPreP is localized to the mitochondrial matrix. In situ immuno-inactivation studies in human brain mitochondria using anti-hPreP antibodies showed complete inhibition of proteolytic activity against Abeta. We have cloned, overexpressed, and purified recombinant hPreP and its mutant with catalytic base Glu(78) in the inverted zinc-binding motif replaced by Gln. In vitro studies using recombinant hPreP and liquid chromatography nanospray tandem mass spectrometry revealed novel cleavage specificities against Abeta-(1-42), Abeta-(1-40), and Abeta Arctic, a protein that causes increased protofibril formation an early onset familial variant of Alzheimer disease. In contrast to insulin degrading enzyme, which is a functional analogue of hPreP, hPreP does not degrade insulin but does degrade insulin B-chain. Molecular modeling of hPreP based on the crystal structure at 2.1 A resolution of AtPreP allowed us to identify Cys(90) and Cys(527) that form disulfide bridges under oxidized conditions and might be involved in redox regulation of the enzyme. Degradation of the mitochondrial Abeta by hPreP may potentially be of importance in the pathology of Alzheimer disease.
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| 4. |
- Gurmu, Daniel, et al.
(författare)
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The crystal structure of the protein YhaK from Escherichia coli reveals a new subclass of redox sensitive enterobacterial bicupins
- 2009
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Ingår i: Proteins. - : Wiley. - 0887-3585 .- 1097-0134. ; 74:1, s. 18-31
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Tidskriftsartikel (refereegranskat)abstract
- YhaK is a protein of unknown function found in low abundance in the cytosol of Escherichia coli. DNA array studies have revealed that YhaK is strongly up-regulated by nitroso-glutathione (GSNO) and also displays a 12-fold increase in expression during biofilm growth of E. coli 83972 and VR50 in human urine. We have determined the YhaK crystal structure and demonstrated that in vitro YhaK is a good marker for monitoring oxidative stresses in E. coli. The YhaK protein structure shows a bicupin fold where the two cupin domains are crosslinked with one intramolecular disulfide bond (Cys10 to Cys204). We found that the third cysteine in YhaK, Cys122, is oxidized to a sulfenic acid. Two chloride ions are found in the structure, one close to the reactive Cys122, and the other on a hydrophobic surface close to a symmetry-related molecule. There are major structural differences at the N-terminus of YhaK compared with similar structures that also display the bicupin fold (YhhW and hPirin). YhaK showed no quercetinase and peroxidase activity. However, reduced YhaK was very sensitive to reactive oxygen species (ROS). The complete, functional E. coli glutaredoxin or thioredoxin systems protected YhaK from oxidation. E. coli thioredoxin reductase and NADPH produced ROS and caused oxidation and oligomerization of reduced YhaK. Taken together, we propose that YhaK is the first of a new sub-class of bicupins that lack the canonical cupin metal-binding residues of pirins and may be involved in chloride binding and/or sensing of oxidative stress in enterobacteria.
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| 5. |
- Johnson, Kenneth A, et al.
(författare)
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The closed structure of presequence protease PreP forms a unique 10,000 Angstroms3 chamber for proteolysis.
- 2006
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Ingår i: EMBO J. - : Wiley. - 0261-4189 .- 1460-2075. ; 25:9, s. 1977-86
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Tidskriftsartikel (refereegranskat)abstract
- Presequence protease PreP is a novel protease that degrades targeting peptides as well as other unstructured peptides in both mitochondria and chloroplasts. The first structure of PreP from Arabidopsis thaliana refined at 2.1 Angstroms resolution shows how the 995-residue polypeptide forms a unique proteolytic chamber of more than 10,000 Angstroms(3) in which the active site resides. Although there is no visible opening to the chamber, a peptide is bound to the active site. The closed conformation places previously unidentified residues from the C-terminal domain at the active site, separated by almost 800 residues in sequence to active site residues located in the N-terminal domain. Based on the structure, a novel mechanism for proteolysis is proposed involving hinge-bending motions that cause the protease to open and close in response to substrate binding. In support of this model, cysteine double mutants designed to keep the chamber covalently locked show no activity under oxidizing conditions. The manner in which substrates are processed inside the chamber is reminiscent of the proteasome; therefore, we refer to this protein as a peptidasome.
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| 6. |
- Lillbacka, Robert, 1974, et al.
(författare)
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Cyclic stress-strain behavior and load sharing in duplex stainless steels: Aspects of modeling and experiments
- 2007
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Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454. ; 55:16, s. 5359-5368
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Tidskriftsartikel (refereegranskat)abstract
- From cyclic experimental tests, it has been found that the cyclic stress-strain behavior of duplex stainless steels (DSSs) is largely dependent on the applied load/strain amplitude. It is believed that the difference in the elastoplastic properties between the austenite and ferrite phases as well as the load sharing between the phases, are responsible for the dependence. In order to examine this hypothesis, three different DSSs, where the difference in the elastoplastic properties between the phases varies between them, are studied in this paper. The examinations are performed both experimentally and by simulations using multiscale material modeling. Since multiscale material modeling is used, it is possible to study in more detail the stress-strain evolution in the two phases during cycling. It is found that the difference in the elastoplastic properties between the phases affects the amount of plastic deformation occurring in the austenite and ferrite phases of the three steels. As a consequence, the cyclic stress-strain behavior is different in the three steels. A more detailed analysis of the dislocation structures formed in the two phases is also performed, and it is found that the slip band formation and the dislocation structures strongly depend on the elastoplastic properties of the individual phases as well as on the load sharing between the phases. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 7. |
- Milani, Tommaso M., 1973-
(författare)
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Debating Swedish : Language Politics and Ideology in Contemporary Sweden
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is concerned with three language debates that reached their most crucial peaks in Sweden at the beginning of the twenty-first century: (i) the debate on the promotion of the Swedish language, (ii) the debate on language testing for citizenship, and (iii) the debate on mother tongue instruction. The main scope of the thesis is to take a theoretically multi-pronged approach to these debates trying to shed light on the following aspects: Why did such debates emerge when they did? Which discourses were available in those specific historical moments? Who are the social actors that intervened in these debates? What is at stake for them? What do they claim? What systems of values, ideas and beliefs – i.e. ideologies – underlie such claims? What are the effects in terms of identities, objects of political intervention, commonsensical knowledge and authority that these discourses and ideologies produce?Taking Sweden as a case in point, the thesis adds to the existing literature another example of how language debates are the manifestation of conflicts between different language ideologies that struggle for hegemony, thus attempting to impose one specific way of envisaging the management of a nation-state in a time of globalisation. In their outer and most patent facets, these struggles deal with the relationships between languages in today’s Sweden, and how the state, through legislation, should – or should not – regulate such relationships in order to (re)produce some kind of linguistic order. However, the thesis also illustrates that when social actors appeal to a linguistic order, they not only draw boundaries between different languages in a given society, but they also bring into existence a social world in which the speakers of those languages come to occupy specific social positions. These linguistic and social hierarchies, in turn, are imbricated in an often implicit moral regime of what counts as good or bad, acceptable or taboo in that society.
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| 8. |
- Moss, Brian D., et al.
(författare)
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Climate change and the future of freshwater biodiversity in Europe : a primer for policy-makers
- 2009
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Ingår i: Freshwater Reviews. - : Freshwater Biological Association. - 1755-084X. ; 2:2, s. 103-130
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Tidskriftsartikel (refereegranskat)abstract
- Earth's climate is changing, and by the end of the 21st century in Europe, average temperatures are likely to have risen by at least 2 °C, and more likely 4 °C with associated effects on patterns of precipitation and the frequency of extreme weather events. Attention among policy-makers is divided about how to minimise the change, how to mitigate its effects, how to maintain the natural resources on which societies depend and how to adapt human societies to the changes. Natural systems are still seen, through a long tradition of conservation management that is largely species-based, as amenable to adaptive management, and biodiversity, mostly perceived as the richness of plant and vertebrate communities, often forms a focus for planning. We argue that prediction of particular species changes will be possible only in a minority of cases but that prediction of trends in general structure and operation of four generic freshwater ecosystems (erosive rivers, depositional floodplain rivers, shallow lakes and deep lakes) in three broad zones of Europe (Mediterranean, Central and Arctic-Boreal) is practicable. Maintenance and rehabilitation of ecological structures and operations will inevitably and incidentally embrace restoration of appropriate levels of species biodiversity. Using expert judgement, based on an extensive literature, we have outlined, primarily for lay policy makers, the pristine features of these systems, their states under current human impacts, how these states are likely to alter with a warming of 2 °C to 4 °C and what might be done to mitigate this. We have avoided technical terms in the interests of communication, and although we have included full referencing as in academic papers, we have eliminated degrees of detail that could confuse broad policy-making
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| 9. |
- Wallentin, Carl-Johan, et al.
(författare)
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Network analysis of bicyclo 3.3.1 nonanes: the diol, the dione and the acetal
- 2009
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 11:9, s. 1837-1841
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Tidskriftsartikel (refereegranskat)abstract
- The solid state structure of endo,endo-bicyclo[3.3.1]nonane-2,6-diol, rac-2, shows a hydrogen bonded, three-connected, chiral 3D-net with utg-topology, distinctively different from those formed by the so called tubuland diols, e.g. 2,6-dimethylbicyclo[3.3.1]nonane-exo2, exo-6-diol, rac-5, that crystallise as three-connected, chiral etanets and from the qtz-net formed by weaker hydrogen bonds in the bicyclo[3.3.1]nonane-2,6-dione, 3. The protected bicyclo[3.3.1]nonane2,6-dione, bis-2,6-ethylenedioxy acetal, 4, has a structure governed by weaker forces and can be interpreted as close packed stacks.
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