Superoxide anion generation by the cytochrome bc1 complex
Superoxide anion generation by the cytochrome bc1 complex
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DOI：
10.1016/j.abb.2003.08.028
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发表时间：
2003-11-15
影响因子：
3.9
通讯作者：
Trumpower, BL
中科院分区：
文献类型：
--
作者：
Sun, H;Trumpower, BL
我们测量了细胞色素be（从牛心脏和酵母线粒体中分离出的复合物）和细胞色素be（来自酵母突变体的复合物）产生的超氧阴离子的速率，其中细胞色素b血红素和Rieske铁硫簇的中点电位因这些蛋白质的突变而改变。对于所有be，复合物，在不存在bc(1)抑制剂的情况下，超氧阴离子产生速率最大，并且范围为细胞色素c还原速率的3%至5%。豆黄素（Stigmatellin）是一种与 be 复合物中泛醇氧化位点结合的抑制剂，消除了超氧阴离子的形成，而 myxothiazol（另一种泛醇氧化抑制剂）则允许超氧阴离子以低速率形成。抗霉素是一种与 be, 复合物中泛醌还原位点结合的抑制剂，也允许超氧阴离子形成，且形成速度比 myxothiazol 稍高。细胞色素b血红素中点电位的变化对细胞色素c还原速率没有显着影响，对超氧阴离子形成速率只有很小的影响。 Rieske铁硫蛋白的突变将其中点电位从+285mV降低至+220mV，导致超氧阴离子速率下降，同时细胞色素e还原酶活性下降。这些结果表明超氧阴离子在哺乳动物和酵母复合物中通过相似的机制形成。结果还表明，在泛醇氧化过程中接受电子的氧化还原组分的中点电位的变化对超氧阴离子的形成只有很小的影响，除了影响酶的活性之外。 (C) 2003 Elsevier Inc. 保留所有权利。
We have measured the rates of superoxide anion generation by cytochrome be, complexes isolated from bovine heart and yeast mitochondria, and by cytochrome be, complexes from yeast mutants in which the midpoint potentials of the cytochrome b hemes and the Rieske iron-sulfur cluster were altered by mutations in those proteins. With all of the be, complexes the rate of superoxide anion production was greatest in the absence of bc(1) inhibitor and ranged from 3% to 5% of the rate of cytochrome c reduction. Stigmatellin, an inhibitor that binds to the ubiquinol oxidation site in the be, complex, eliminated superoxide anion formation, while myxothiazol, another inhibitor of ubiquinol oxidation, allowed superoxide anion formation at a low rate. Antimycin, an inhibitor that binds to the ubiquinone reduction site in the be, complex, also allowed superoxide anion formation and at a slightly greater rate than myxothiazol. Changes in the midpoint potentials of the cytochrome b hemes had no significant effect on the rate of cytochrome c reduction and only a small effect on the rate of superoxide anion formation. A mutation in the Rieske iron-sulfur protein that lowers its midpoint potential from +285 to +220mV caused the rate of superoxide anion to decline in parallel with a decline in cytochrome e reductase activity. These results indicate that superoxide anion is formed by similar mechanisms in mammalian and yeast be, complexes. The results also show that changes in the midpoint potentials of the redox components that accept electrons during ubiquinol oxidation have only small effects on the formation of superoxide anion, except to the extent that they affect the activity of the enzyme. (C) 2003 Elsevier Inc. All rights reserved.