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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Direct observation of protonation reactions during the catalytic cycle of cytochrome c oxidase.
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Direct observation of protonation reactions during the catalytic cycle of cytochrome c oxidase.

机译：直接观察细胞色素C氧化酶催化循环中的质子化反应。

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摘要

Cytochrome c oxidase, the terminal protein in the respiratory chain, converts oxygen into water and helps generate the electrochemical gradient used in the synthesis of ATP. The catalytic action of cytochrome c oxidase involves electron transfer, proton transfer, and O2 reduction. These events trigger specific molecular changes at the active site, which, in turn, influence changes throughout the protein, including alterations of amino acid side chain orientations, hydrogen bond patterns, and protonation states. We have used IR difference spectroscopy to investigate such modulations for the functional intermediate states E, R2,Pm, and F. These spectra reveal deprotonation of its key glutamic acid E286 in the E and in the Pm states. The consecutive deprotonation and reprotonation of E286 twice within one catalytic turnover illustrates the role of this residue as a proton shuttle. In addition, the spectra point toward deprotonation of a redox-active tyrosine, plausibly Y288, in the F intermediate. Structural insights into the molecular mechanism of catalysis based on the subtle molecular changes observed with IR difference spectroscopy are discussed.
机译：细胞色素c氧化酶是呼吸链中的末端蛋白，可将氧气转化为水，并有助于生成用于ATP合成的电化学梯度。细胞色素C氧化酶的催化作用包括电子转移，质子转移和O2还原。这些事件在活性位点触发特定的分子变化，进而影响整个蛋白质的变化，包括氨基酸侧链方向，氢键模式和质子化状态的改变。我们已经使用红外差光谱法研究了功能性中间态E，R2，Pm和F的这种调制。这些光谱揭示了其关键的谷氨酸E286在E和Pm态的去质子化。 E286在一次催化转换中连续两次进行去质子化和再质子化，说明该残基作为质子穿梭的作用。此外，光谱指向F中间体中的氧化还原活性酪氨酸（可能是Y288）的去质子化。讨论了基于红外差光谱观察到的细微分子变化的催化分子机理的结构见解。

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