A peroxide bridge between Fe and Cu ions in the O2 reduction site of fully oxidized cytochrome c oxidase could suppress the proton pump
A peroxide bridge between Fe and Cu ions in the O2 reduction site of fully oxidized cytochrome c oxidase could suppress the proton pump
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DOI：
10.1073/pnas.0806391106
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发表时间：
2009-02-17
影响因子：
11.1
通讯作者：
Yoshikawa, Shinya
中科院分区：
文献类型：
--
作者：
Aoyama, Hiroshi;Muramoto, Kazumasa;Yoshikawa, Shinya
细胞色素c氧化酶的完全氧化形式在完全还原形式完全氧化后立即在最初的2个单电子还原步骤中的每一个步骤中泵送质子，而在完全氧化的“分离形式”的单电子还原期间不泵送质子（没有任何还原/氧化处理的完全氧化形式）[Bloch D等人（2004）The catalytic cycle of cytochrome c oxidase is not the sum of its two halves. Proc Natl Acad Sci USA 101：529-533]。为了鉴定导致这2种不同的完全氧化形式之间显著功能差异的结构差异，通过限制每次发射的X射线剂量和使用许多（约400个）单晶，以1.95埃分辨率测定了完全氧化的分离牛心脏细胞色素c氧化酶的X射线结构。这最小化了由X射线照射引起的水合电子的影响。X-射线结构显示过氧化物基团桥接O-2还原位点中的2个金属位点（Fe 3 +-O-O--Cu 2+），与从完全还原形式完全氧化后立即完全氧化形式的氢氧化铁（Fe 3 +-OH-）相反，如共振拉曼分析所揭示的。过氧化物桥连结构与还原滴定结果一致，表明完全氧化的分离形式完全还原需要6个电子当量。2种完全氧化形式之间的结构差异表明，O-2还原位点中的结合过氧化物抑制质子泵功能。
The fully oxidized form of cytochrome c oxidase, immediately after complete oxidation of the fully reduced form, pumps protons upon each of the initial 2 single-electron reduction steps, whereas protons are not pumped during single-electron reduction of the fully oxidized "as-isolated'' form (the fully oxidized form without any reduction/oxidation treatment) [Bloch D, et al. (2004) The catalytic cycle of cytochrome c oxidase is not the sum of its two halves. Proc Natl Acad Sci USA 101:529-533]. For identification of structural differences causing the remarkable functional difference between these 2 distinct fully oxidized forms, the X-ray structure of the fully oxidized as-isolated bovine heart cytochrome c oxidase was determined at 1.95-angstrom resolution by limiting the X-ray dose for each shot and by using many (approximate to 400) single crystals. This minimizes the effects of hydrated electrons induced by the X-ray irradiation. The X-ray structure showed a peroxide group bridging the 2 metal sites in the O-2 reduction site (Fe3+-O--O--Cu2+), in contrast to a ferric hydroxide (Fe3+-OH-) in the fully oxidized form immediately after complete oxidation from the fully reduced form, as has been revealed by resonance Raman analyses. The peroxide-bridged structure is consistent with the reductive titration results showing that 6 electron equivalents are required for complete reduction of the fully oxidized as-isolated form. The structural difference between the 2 fully oxidized forms suggests that the bound peroxide in the O-2 reduction site suppresses the proton pumping function.