Substrate redox potential controls superoxide production kinetics in the cytochrome bc complex.
Substrate redox potential controls superoxide production kinetics in the cytochrome bc complex.
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DOI：
10.1021/bi901205w
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发表时间：
2009-11-17
期刊：
影响因子：
2.9
通讯作者：
Bowman, Michael K.
中科院分区：
文献类型：
--
作者：
Cape, Jonathan L.;Aidasani, Divesh;Kramer, David M.;Bowman, Michael K.
细胞色素bc1复合体的q循环机制使泛醇到细胞色素c（或其他生理受体）的电子传递过程中的能量转换最大化。然而，q周期的重要步骤仍然存在激烈的争论，包括：分岔电子传递；尽管可能发生短路和旁路反应，但q循环的产率高，特异性强；喹啉氧化过程中可观察到的中间体的稀缺性。越来越多的证据表明，在Qo位点氧化喹啉过程中产生超氧化物的一些旁路反应在分叉反应的较晚阶段偏离了q循环，这为研究q循环的初始反应提供了一种额外的手段。旁路反应为控制和操纵反应条件（如氧化还原电位）提供了更大的空间，因为它们有效地将q循环初始反应与后续步骤分离或解耦，避免了许多并发症和相互作用。我们研究了酵母细胞色素bc1复合体的氧化速率对底物氧化还原电位的依赖性，发现速率限制发生在Rieske蛋白将喹啉直接单电子氧化成半醌的水平。半醌的氧化和细胞b或O2的减少是随后的，不同的步骤。这些实验结果与电子转移到Rieske蛋白并不是电子转移到细胞色素b之前的一个明显步骤的模型不相容，也与构象门控模型不相容，构象门控模型通过与正常q -循环不同的限速反应产生超氧化物。
The Q-cycle mechanism of the cytochrome bc1 complex maximizes energy conversion during electron transport from ubiquinol to cytochrome c (or alternate physiological acceptors). Yet important steps in the Q-cycle are still hotly debated including: bifurcated electron transport; the high yield and specificity of the Q-cycle despite possible short circuits and bypass reactions; and the rarity of observable intermediates in the oxidation of quinol. Mounting evidence shows that some bypass reactions producing superoxide during oxidation of quinol at the Qo site diverge from the Q-cycle rather late in the bifurcated reaction and provide an additional means of studying initial reactions of the Q-cycle. Bypass reactions offer more scope for controlling and manipulating reaction conditions, e.g., redox potential, because they effectively isolate or decouple the Q-cycle initial reactions from later steps, avoiding many complications and interactions. We examine the dependence of oxidation rate on substrate redox potential in the yeast cytochrome bc1 complex and find that the rate limitation occurs at the level of direct one-electron oxidation of quinol to semiquinone by the Rieske protein. Oxidation of semiquinone and reduction of cyt b or O2 are subsequent, distinct steps. These experimental results are incompatible with models in which electron transfer to the Rieske protein is not a distinct step preceding electron transfer to cytochrome b, and with conformational gating models that produce superoxide by different rate limiting reactions from the normal Q-cycle.
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影响因子：
4.8
作者：
Cape, JL;Strahan, JR;Kramer, DM
通讯作者：
Kramer, DM
影响因子：
2.9
作者：
Cooley, JW;Roberts, AG;Daldal, F
通讯作者：
Daldal, F
DOI：
10.1016/0005-2728(90)90082-f
发表时间：
1990-02-22
期刊：
BIOCHIMICA ET BIOPHYSICA ACTA
影响因子：
--
作者：
GU, LQ;YU, L;YU, CA
通讯作者：
YU, CA
影响因子：
15
作者：
Cape, JL;Bowman, MK;Kramer, DM
通讯作者：
Kramer, DM
影响因子：
3
作者：
Darrouzet, E;Valkova-Valchanova, M;Daldal, F
通讯作者：
Daldal, F