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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >A single-amino-acid lid renders a gas-tight compartment within a membrane-bound transporter.
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A single-amino-acid lid renders a gas-tight compartment within a membrane-bound transporter.

机译：单个氨基酸的盖子在膜结合的转运蛋白内形成气密隔室。

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摘要

Proteins undergo structural fluctuations between nearly isoenergetic substates. Such fluctuations are often intimately linked with the functional properties of proteins. However, in some cases, such as in transmembrane ion transporters, the control of the ion transport requires that the protein is designed to restrict the motions in specific regions. In this study, we have investigated the dynamics of a membrane-bound respiratory oxidase, which acts both as an enzyme catalyzing reduction of O(2) to H(2)O and as a transmembrane proton pump. The segment of the protein where proton translocation is controlled ("gating" region) overlaps with a channel through which O(2) is delivered to the catalytic site. We show that the replacement of an amino acid residue with a small side chain (Gly) by one with a larger side chain (Val), in a narrow part of this channel, completely blocks the O(2) access to the catalytic site and results in formation of a compartment around the site that is impermeable to small gas molecules. Thus, the protein motions cannot counter the blockage introduced by the mutation. These results indicate that the protein motions are restricted in the proton-gating region and that rapid O(2) delivery to the catalytic site requires a gas channel, which is confined within a rigid protein body.
机译：蛋白质在几乎同能的亚状态之间经历结构波动。这种波动通常与蛋白质的功能特性密切相关。但是，在某些情况下，例如在跨膜离子转运蛋白中，对离子转运的控制需要设计蛋白质来限制特定区域的运动。在这项研究中，我们研究了膜结合呼吸氧化酶的动力学，该酶既充当催化O（2）还原为H（2）O的酶，又充当跨膜质子泵。质子转运受控制的蛋白质部分（“门控”区域）与O（2）通过其传递至催化位点的通道重叠。我们显示，在此通道的狭窄部分中，氨基酸残基由较小的侧链（Gly）替换为具有较大的侧链（Val）的氨基酸残基，完全阻断了O（2）进入催化位点并导致在小气体分子不可渗透的部位周围形成隔室。因此，蛋白质运动不能抵消突变引入的阻断作用。这些结果表明，蛋白质运动在质子门控区域受到限制，快速O（2）传递到催化部位需要气体通道，该通道被限制在刚性蛋白质体内。

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