Winkler, Jay R. and Wittung-Stafshede, Pernilla and Leckner, Johan and Malmström, Bo G. and Gray, Harry B. (1997) Effects of folding on metalloprotein active sites. Proceedings of the National Academy of Sciences of the United States of America, 94 (9). pp. 4246-4249. ISSN 0027-8424 http://resolver.caltech.edu/CaltechAUTHORS:WINpnas97
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Experimental data for the unfolding of cytochrome c and azurin by quanidinium chloride (GuHCl) are used to construct free-energy diagrams for the folding of the oxidized and reduced proteins. With cytochrome c, the driving force for folding the reduced protein is larger than that for the oxidized form. Both the oxidized and the reduced folded forms of yeast cytochrome c are less stable than the corresponding states of the horse protein. Due to the covalent attachment of the heme and is fixed tetragonal coordination geometry, cytochrome c folding can be described by a two-state model. A thermodynamic cycle leads to an expression for the difference in self-exchange reorganization energies for the folded and unfolded proteins. The reorganization energy for electron exchange in the folded protein is approximately 0.5 eV smaller than that for a heme in aqueous solution. The finding that reduced azurin unfolds at lower GuHCl concentrations than the oxidized protein suggests that the coordination structure of copper is different in oxidized and reduced unfolded states: it is likely that the geometry of Cu-I in the unfolded protein is linear or trigonal, whereas Cu-II prefers to be tetragonal. The evidence indicates that protein folding lowers the azurin reorganization energy by roughly 1.7 eV relative to an aqueous Cu(1,10-phenanthroline)(2)(2+/+) reference system.
|Additional Information:||Copyright © 1997 by the National Academy of Sciences. Contributed by Harry B. Gray, February 28, 1997. We thank N. Sutin and E. I. Solomon for helpful comments. This work was supported by the National Science Foundation (MCB9630465), National Institutes of Health (DK19038), and Natural Science Research Council (Sweden). The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.|
|Subject Keywords:||protein folding, rack formation, cytochrome c, azurin, electron transfer, electron-transfer reactions, transfer self-exchange, blue-copper proteins, complexes|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||22 Nov 2005|
|Last Modified:||26 Dec 2012 08:42|
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