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The role of a disulfide bridge in the stability and folding kinetics of Arabidopsis thaliana cytochrome c6A

Mason, Jody M and Bendall, Derek S and Howe, Christopher J and Worrall, Jonathan AR (2012) 'The role of a disulfide bridge in the stability and folding kinetics of Arabidopsis thaliana cytochrome c6A.' Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics, 1824 (2). pp. 311-318. ISSN 1570-9639

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Cytochrome c 6A is a eukaryotic member of the Class I cytochrome c family possessing a high structural homology with photosynthetic cytochrome c 6 from cyanobacteria, but structurally and functionally distinct through the presence of a disulfide bond and a heme mid-point redox potential of + 71 mV (vs normal hydrogen electrode). The disulfide bond is part of a loop insertion peptide that forms a cap-like structure on top of the core α-helical fold. We have investigated the contribution of the disulfide bond to thermodynamic stability and (un)folding kinetics in cytochrome c 6A from Arabidopsis thaliana by making comparison with a photosynthetic cytochrome c 6 from Phormidium laminosum and through a mutant in which the Cys residues have been replaced with Ser residues (C67/73S). We find that the disulfide bond makes a significant contribution to overall stability in both the ferric and ferrous heme states. Both cytochromes c 6A and c 6 fold rapidly at neutral pH through an on-pathway intermediate. The unfolding rate for the C67/73S variant is significantly increased indicating that the formation of this region occurs late in the folding pathway. We conclude that the disulfide bridge in cytochrome c 6A acts as a conformational restraint in both the folding intermediate and native state of the protein and that it likely serves a structural rather than a previously proposed catalytic role. © 2011 Elsevier B.V. All rights reserved.

Item Type: Article
Uncontrolled Keywords: Cytochrome c(6A); Disulfide bond; Protein folding; Heme redox potential
Subjects: Q Science > Q Science (General)
Divisions: Faculty of Science and Health
Faculty of Science and Health > Life Sciences, School of
SWORD Depositor: Elements
Depositing User: Elements
Date Deposited: 19 Jan 2012 13:29
Last Modified: 15 Jan 2022 00:34

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