Influence of Reduction of Heme a and CuA on the Oxidized Catalytic Center of Cytochrome c Oxidase: Insight from Organic Solvents

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• 作者：Marian Fabian ; Daniel Jancura ; Martin Bona ; Andrej Musatov ; Miroslav Baran ; and Graham Palmer
• 刊名：Biochemistry
• 出版年：2006
• 出版时间：April 4, 2006
• 年：2006
• 卷：45
• 期：13
• 页码：4277 - 4283
• 全文大小：82K
• 年卷期：v.45,no.13(April 4, 2006)
• ISSN：1520-4995

文摘

Purified bovine heart cytochrome c oxidase (CcO) has been extracted from aqueous solutioninto hexane in the presence of phospholipids and calcium ions. In extracts, CcO is in the so-called "slow"form and probably situated in reverse micelles. At low water:phospholipid molar ratios, electron transferfrom reduced heme a and Cu_A to the catalytic center is inhibited and both heme a₃ and Cu_B remain in theoxidized state. The rate of binding of cyanide to heme a₃ in this oxidized catalytic center is, however,dependent on the redox state of heme a and Cu_A. When heme a and Cu_A are reduced, the rate is increased20-fold compared to the rate when these two centers are oxidized. The enhanced rate of binding of cyanideto heme a₃ is explained by the destabilization of an intrinsic ligand, located at the catalytic site, that istriggered by the reduction of heme a and Cu_A.