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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Gating of proton and water transfer in the respiratory enzyme cytochrome c oxidase
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Gating of proton and water transfer in the respiratory enzyme cytochrome c oxidase

机译：质子的门控和呼吸酶细胞色素C氧化酶中的水转移

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摘要

The membrane-bound enzyme cytochrome c oxidase is responsible for cell respiration in aerobic organisms and conserves free energy from O_2 reduction into an electrochemical proton gradient by coupling the redox reaction to proton-pumping across the membrane. O_2 reduction produces water at the bimetallic heme a_3/ CUB active site next to a hydrophobic cavity deep within the membrane. Water molecules in this cavity have been suggested to play an important role in the proton-pumping mechanism. Here, we show by molecular dynamics simulations that the conserved arginine/ heme a_3 Δ-propionate ion pair provides a gate, which exhibits reversible thermal opening that is governed by the redox state and the water molecules in the cavity. An important role of this gate in the proton-pumping mechanism is supported by site-directed mutagenesis experiments. Transport of the product water out of the enzyme must be rigidly controlled to prevent water-mediated proton leaks that could compromise the proton-pumping function. Exit of product water is observed through the same arginine/ propionate gate, which provides an explanation for the observed extraordinary spatial specificity of water expulsion from the enzyme.
机译：膜结合酶细胞色素C氧化酶负责好氧生物中的细胞呼吸，并通过将氧化还原反应与跨膜的质子泵送耦合而将O_2还原成电化学质子梯度的自由能得以保留。 O_2还原会在双金属血红素a_3 / CUB活性位点附近的膜内深处的疏水腔处产生水。有人建议在这个腔中的水分子在质子泵浦机制中起重要作用。在这里，我们通过分子动力学模拟表明，保守的精氨酸/血红素a_3Δ-丙酸根离子对提供了一个门，该门显示出可逆的热开口，该开口由氧化还原状态和空腔中的水分子控制。定点诱变实验支持了该门在质子泵浦机制中的重要作用。必须严格控制产品水从酶中的运输，以防止水介导的质子泄漏，该泄漏可能会损害质子泵功能。通过相同的精氨酸/丙酸门观察到产物水的排出，这为观察到的从酶中排出水的非凡的空间特异性提供了解释。

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