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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Structural Basis For Membrane Binding And Catalytic Activation Of The Peripheral Membrane Enzyme Pyruvate Oxidase From Escherichia Coli
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Structural Basis For Membrane Binding And Catalytic Activation Of The Peripheral Membrane Enzyme Pyruvate Oxidase From Escherichia Coli

机译：大肠杆菌外围膜酶丙酮酸氧化酶的膜结合和催化活化的结构基础

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摘要

The thiamin- and flavin-dependent peripheral membrane enzyme pyruvate oxidase from E. coli catalyzes the oxidative decarboxyl-ation of the central metabolite pyruvate to CO_2 and acetate. Concomitant reduction of the enzyme-bound flavin triggers membrane binding of the C terminus and shuttling of 2 electrons to ubiquinone 8, a membrane-bound mobile carrier of the electron transport chain. Binding to the membrane in vivo or limited proteolysis in vitro stimulate the catalytic proficiency by 2 orders of magnitude. The molecular mechanisms by which membrane binding and activation are governed have remained enigmatic. Here, we present the X-ray crystal structures of the full-length enzyme and a proteolytically activated truncation variant lacking the last 23 C-terminal residues inferred as important in membrane binding. In conjunction with spectroscopic results, the structural data pinpoint a conformational rearrangement upon activation that exposes the autoinhibitory C terminus, thereby freeing the active site. In the activated enzyme, Phe-465 swings into the active site and wires both cofactors for efficient electron transfer. The isolated C terminus, which has no intrinsic helix propensity, folds into a helical structure in the presence of micelles.
机译：来自大肠杆菌的硫胺素和黄素依赖性外周膜酶丙酮酸氧化酶催化中央代谢物丙酮酸的氧化脱羧反应生成CO_2和乙酸盐。与酶结合的黄素的同时还原会触发C末端的膜结合，并使2个电子穿梭到泛醌8（泛素8），这是电子传输链的膜结合移动载体。体内结合到膜上或体外有限的蛋白水解作用将催化能力提高了2个数量级。控制膜结合和激活的分子机制仍然是个谜。在这里，我们介绍了全长酶的X射线晶体结构和蛋白水解激活的截断变体，缺少最后23个C端残基，这被认为对膜结合很重要。结合光谱结果，结构数据可在激活时确定构象重排，从而暴露出自抑制性C末端，从而释放出活性位点。在活化的酶中，Phe-465进入活性位点并连接两个辅助因子以实现有效的电子转移。没有内在的螺旋倾向的分离的C末端在存在胶束的情况下会折叠成螺旋结构。

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