文章基本信息

标题：Bovine cytochrome c oxidase structures enable O2 reduction with minimization of reactive oxygens and provide a proton-pumping gate
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作者：Kazumasa Muramoto ; Kazuhiro Ohta ; Kyoko Shinzawa-Itoh 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2010
卷号：107
期号：17
页码：7740-7745
DOI：10.1073/pnas.0910410107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The O2 reduction site of cytochrome c oxidase (CcO), comprising iron (Fea3) and copper (CuB) ions, is probed by x-ray structural analyses of CO, NO, and CN- derivatives to investigate the mechanism of the complete reduction of O2. Formation of the [IMG]/medium/pnas.0910410107eq1.gif" ALT="Formula "> derivative contributes to the trigonal planar coordination of [IMG]/medium/pnas.0910410107eq2.gif" ALT="Formula "> and displaces one of its three coordinated imidazole groups while a water molecule becomes hydrogen bonded to both the CN- ligand and the hydroxyl group of Tyr244. When O2 is bound to [IMG]/medium/pnas.0910410107eq3.gif" ALT="Formula ">, it is negatively polarized ([IMG]/medium/pnas.0910410107eq4.gif" ALT="Formula ">), and expected to induce the same structural change induced by CN-. This structural change allows [IMG]/medium/pnas.0910410107eq5.gif" ALT="Formula "> to receive three electron equivalents nonsequentially from [IMG]/medium/pnas.0910410107eq6.gif" ALT="Formula ">, [IMG]/medium/pnas.0910410107eq7.gif" ALT="Formula ">, and Tyr-OH, providing complete reduction of O2 with minimization of production of active oxygen species. The proton-pumping pathway of bovine CcO comprises a hydrogen-bond network and a water channel which extend to the positive and negative side surfaces, respectively. Protons transferred through the water channel are pumped through the hydrogen-bond network electrostatically with positive charge created at the Fea center by electron donation to the O2 reduction site. Binding of CO or NO to [IMG]/medium/pnas.0910410107eq8.gif" ALT="Formula "> induces significant narrowing of a section of the water channel near the hydrogen-bond network junction, which prevents access of water molecules to the network. In a similar manner, O2 binding to [IMG]/medium/pnas.0910410107eq9.gif" ALT="Formula "> is expected to prevent access of water molecules to the hydrogen-bond network. This blocks proton back-leak from the network and provides an efficient gate for proton-pumping.
关键词：cell respiration ; heme copper protein ; membrane protein ; respiratory inhibitor ; x-ray structural analysis