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首页> 外文期刊>Biochemistry >Cu XAS shows a change in the ligation of CuB upon reduction of cytochrome bo3 from Escherichia coli.
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Cu XAS shows a change in the ligation of CuB upon reduction of cytochrome bo3 from Escherichia coli.

机译：Cu XAS在还原大肠杆菌细胞色素bo3后显示CuB连接的变化。

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Copper X-ray absorption spectroscopy (XAS) has been used to examine the structures of the Cu(II) and Cu(I) forms of the cytochrome bo3 quinol oxidase from Escherichia coli. Cytochrome bo3 is a member of the superfamily of heme-copper respiratory oxidases. Of particular interest is the fact that these enzymes function as redox-linked proton pumps, resulting in the net translocation of one H+ per electron across the membrane. The molecular mechanism of how this pump operates and the manner by which it is linked to the oxygen chemistry at the active site of the enzyme are unknown. Several proposals have featured changes in the coordination of CuB during enzyme turnover that would result in sequential protonation or deprotonation events that are key to the functioning proton pump. This would imply lability of the ligands to CuB. In this work, the structure of the protein in the immediate vicinity of CuB, in both the fully oxidized and fully reduced forms of the enzyme, has been examined by Cu XAS, a technique that is particularly sensitive to changes in metal coordination. The results show that in the oxidized enzyme, CuB(II) is four-coordinate, consistent with three imidazoles and one hydroxyl (or water). Upon reduction of the enzyme, the coordination of CuB(I) is significantly altered, consistent with the loss of one of the histidine imidazole ligands in at least a substantial fraction of the population. These data add to the credibility that changes in the ligation of CuB might occur during catalytic turnover of the enzyme and, therefore, could, in principle, be part of the mechanism of proton pumping.
机译：铜X射线吸收光谱法（XAS）已用于检查来自大肠杆菌的细胞色素bo3喹诺醇氧化酶的Cu（II）和Cu（I）形式的结构。细胞色素bo3是血红素铜呼吸氧化酶超家族的成员。特别令人感兴趣的是，这些酶起着氧化还原连接的质子泵的作用，导致每个电子在膜上净迁移一个H +。该泵如何工作的分子机理以及在酶的活性位点上与氧化学反应的方式尚不清楚。几项提议的特征是酶转换过程中CuB配位的变化，这将导致顺序质子化或去质子化事件，这是功能性质子泵的关键。这将暗示配体对CuB的不稳定性。在这项工作中，已经通过Cu XAS检查了酶完全氧化和完全还原形式的CuB紧邻蛋白质的结构，该技术对金属配位的变化特别敏感。结果表明，在氧化酶中，CuB（II）是四配位的，与三个咪唑和一个羟基（或水）一致。还原酶后，CuB（I）的配比会显着改变，这与至少一部分人口中组氨酸咪唑配体之一的丢失一致。这些数据增加了可信性，即在酶的催化周转过程中可能发生CuB连接的变化，因此，原则上可以成为质子泵送机制的一部分。

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