1ep7: Difference between revisions
New page: left|200px<br /><applet load="1ep7" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ep7, resolution 2.1Å" /> '''CRYSTAL STRUCTURE OF ... |
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[[Image:1ep7.gif|left|200px]]<br /><applet load="1ep7" size=" | [[Image:1ep7.gif|left|200px]]<br /><applet load="1ep7" size="350" color="white" frame="true" align="right" spinBox="true" | ||
caption="1ep7, resolution 2.1Å" /> | caption="1ep7, resolution 2.1Å" /> | ||
'''CRYSTAL STRUCTURE OF WT THIOREDOXIN H FROM CHLAMYDOMONAS REINHARDTII'''<br /> | '''CRYSTAL STRUCTURE OF WT THIOREDOXIN H FROM CHLAMYDOMONAS REINHARDTII'''<br /> | ||
==Overview== | ==Overview== | ||
Thioredoxins are ubiquitous proteins which catalyse the reduction of | Thioredoxins are ubiquitous proteins which catalyse the reduction of disulphide bridges on target proteins. The catalytic mechanism proceeds via a mixed disulphide intermediate whose breakdown should be enhanced by the involvement of a conserved buried residue, Asp-30, as a base catalyst towards residue Cys-39. We report here the crystal structure of wild-type and D30A mutant thioredoxin h from Chlamydomonas reinhardtii, which constitutes the first crystal structure of a cytosolic thioredoxin isolated from a eukaryotic plant organism. The role of residue Asp-30 in catalysis has been revisited since the distance between the carboxylate OD1 of Asp-30 and the sulphur SG of Cys-39 is too great to support the hypothesis of direct proton transfer. A careful analysis of all available crystal structures reveals that the relative positioning of residues Asp-30 and Cys-39 as well as hydrophobic contacts in the vicinity of residue Asp-30 do not allow a conformational change sufficient to bring the two residues close enough for a direct proton transfer. This suggests that protonation/deprotonation of Cys-39 should be mediated by a water molecule. Molecular-dynamics simulations, carried out either in vacuo or in water, as well as proton-inventory experiments, support this hypothesis. The results are discussed with respect to biochemical and structural data. | ||
==About this Structure== | ==About this Structure== | ||
1EP7 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Chlamydomonas_reinhardtii Chlamydomonas reinhardtii]. Full crystallographic information is available from [http:// | 1EP7 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Chlamydomonas_reinhardtii Chlamydomonas reinhardtii]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1EP7 OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: Corbier, C.]] | [[Category: Corbier, C.]] | ||
[[Category: Didierjean, C.]] | [[Category: Didierjean, C.]] | ||
[[Category: Jacquot, J | [[Category: Jacquot, J P.]] | ||
[[Category: Menchise, V.]] | [[Category: Menchise, V.]] | ||
[[Category: Saviano, M.]] | [[Category: Saviano, M.]] | ||
[[Category: electron transport]] | [[Category: electron transport]] | ||
''Page seeded by [http:// | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:30:06 2008'' | ||
Revision as of 13:30, 21 February 2008
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CRYSTAL STRUCTURE OF WT THIOREDOXIN H FROM CHLAMYDOMONAS REINHARDTII
OverviewOverview
Thioredoxins are ubiquitous proteins which catalyse the reduction of disulphide bridges on target proteins. The catalytic mechanism proceeds via a mixed disulphide intermediate whose breakdown should be enhanced by the involvement of a conserved buried residue, Asp-30, as a base catalyst towards residue Cys-39. We report here the crystal structure of wild-type and D30A mutant thioredoxin h from Chlamydomonas reinhardtii, which constitutes the first crystal structure of a cytosolic thioredoxin isolated from a eukaryotic plant organism. The role of residue Asp-30 in catalysis has been revisited since the distance between the carboxylate OD1 of Asp-30 and the sulphur SG of Cys-39 is too great to support the hypothesis of direct proton transfer. A careful analysis of all available crystal structures reveals that the relative positioning of residues Asp-30 and Cys-39 as well as hydrophobic contacts in the vicinity of residue Asp-30 do not allow a conformational change sufficient to bring the two residues close enough for a direct proton transfer. This suggests that protonation/deprotonation of Cys-39 should be mediated by a water molecule. Molecular-dynamics simulations, carried out either in vacuo or in water, as well as proton-inventory experiments, support this hypothesis. The results are discussed with respect to biochemical and structural data.
About this StructureAbout this Structure
1EP7 is a Single protein structure of sequence from Chlamydomonas reinhardtii. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of the wild-type and D30A mutant thioredoxin h of Chlamydomonas reinhardtii and implications for the catalytic mechanism., Menchise V, Corbier C, Didierjean C, Saviano M, Benedetti E, Jacquot JP, Aubry A, Biochem J. 2001 Oct 1;359(Pt 1):65-75. PMID:11563970
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