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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Structure of electron transfer flavoprotein-ubiquinone oxidoreductase and electron transfer to the mitochondrial ubiquinone pool
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Structure of electron transfer flavoprotein-ubiquinone oxidoreductase and electron transfer to the mitochondrial ubiquinone pool

机译：电子转移黄素蛋白-泛醌氧化还原酶的结构和电子转移至线粒体泛醌池

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摘要

Electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO) is a 4Fe4S flavoprotein located in the inner mitochondrial membrane. It catalyzes ubiquinone (UQ) reduction by ETF, linking oxidation of fatty acids and some amino acids to the mitochondrial respiratory chain. Deficiencies in ETF or ETF-QO result in multiple acyl-CoA dehydrogenase deficiency, a human metabolic disease. Crystal structures of ETF-QO with and without bound UQ were determined, and they are essentially identical. The molecule forms a single structural domain. Three functional regions bind FAD, the 4Fe4S cluster, and UQ and are closely packed and share structural elements, resulting in no discrete structural domains. The UQ-binding pocket consists mainly of hydrophobic residues, and UQ binding differs from that of other UQ-binding proteins. ETF-QO is a monotopic integral membrane protein. The putative membrane-binding surface contains an alpha-helix and a beta-hairpin, forming a hydrophobic plateau. The UQ-flavin distance (8.5 angstrom) is shorter than the UQ-cluster distance (18.8 angstrom), and the very similar redox potentials of FAD and the cluster strongly suggest that the flavin, not the cluster, transfers electrons to UQ. Two possible electron transfer paths can be envisioned. First, electrons from the ETF flavin semiquinone may enter the ETF-QO flavin one by one, followed by rapid equilibration with the cluster. Alternatively, electrons may enter via the cluster, followed by equilibration between centers. In both cases, when ETF-QO is reduced to a two-electron reduced state (one electron at each redox center), the enzyme is primed to reduce UQ to ubiquinol via FAD.
机译：电子转移黄素蛋白-泛醌氧化还原酶（ETF-QO）是位于线粒体内膜的4Fe4S黄素蛋白。它通过ETF催化泛醌（UQ）的还原，将脂肪酸和某些氨基酸的氧化与线粒体呼吸链联系起来。 ETF或ETF-QO缺乏会导致多种酰基辅酶A脱氢酶缺乏症，这是一种人类代谢性疾病。确定了具有和不具有结合的UQ的ETF-QO的晶体结构，并且它们基本上是相同的。该分子形成单个结构域。三个功能区绑定FAD，4Fe4S簇和UQ，并且紧密堆积并共享结构元素，因此没有离散的结构域。 UQ结合袋主要由疏水残基组成，并且UQ结合不同于其他UQ结合蛋白。 ETF-QO是一种单位整合膜蛋白。推定的膜结合表面含有形成疏水平台的α-螺旋和β-发夹。 UQ黄素距离（8.5埃）比UQ簇距离（18.8埃）短，FAD和簇的氧化还原电位非常相似，这强烈表明黄素而非簇将电子转移到UQ。可以设想两个可能的电子传输路径。首先，来自ETF黄素半醌的电子可能会一个接一个地进入ETF-QO黄素，然后与簇快速平衡。或者，电子可以通过团簇进入，然后在中心之间达到平衡。在这两种情况下，当ETF-QO还原成两电子还原态（每个氧化还原中心一个电子）时，该酶被引发以通过FAD将UQ还原为泛醇。

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