Binding dynamics at the quinone reduction (Qi) site influence the equilibrium interactions of the iron sulfur protein and hydroquinone oxidation (Qo) site of the cytochrome bc1 complex
Binding dynamics at the quinone reduction (Qi) site influence the equilibrium interactions of the iron sulfur protein and hydroquinone oxidation (Qo) site of the cytochrome bc1 complex
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DOI：
10.1021/bi050571
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发表时间：
2005-08-09
期刊：
影响因子：
2.9
通讯作者：
Daldal, F
中科院分区：
文献类型：
--
作者：
Cooley, JW;Ohnishi, T;Daldal, F
已经报道了多个低电位电子传递途径抑制剂的实例，这些抑制剂在不同程度上影响细胞色素（cyt）bc（1）复合物的结构，从氢醌（QH（2））氧化和cyt c（1）还原动力学的变化到含铁硫亚基（Fe/S蛋白）铰链区的蛋白水解可及性。然而，没有实例已记录的任何随之而来的变化的环境[2Fe-2S]集群。在这项工作中，这个问题得到了详细解决，利用增加的光谱和空间分辨率与取向相关的电子顺磁共振（EPR）光谱分析有序膜制剂。第一次，通过Q（i）位点抑制剂或各种突变的低电位电子传递途径的扰动被证明可以改变Fe/S蛋白的cyt B血红素和[2Fe-2S]簇的EPR谱。特别是，两个相互关联的影响的Q;-网站上的Fe/S亚基的修改，一个改变其[2Fe-2S]簇的局部环境和第二个影响该亚基的流动性，被揭示。值得注意的是，在Q1位点或其附近的不同抑制剂和突变以不同的方式诱导这两种效应，表明在Q1位点发生的事件影响cyt bc的整体结构（1）。此外，离散的Q（i）-位点亚结构域的占用不同地阻碍Fe/S蛋白在Q（o）位点的定位。这些发现使我们提出抗霉素A和HQNO分别模拟了QH（2）和Q在Q（i）位点的存在。这些研究结果的影响，在Q（O）-Q（I）;网站的通信和多个营业额的eyt BC，进行了讨论。
Multiple instances of low-potential electron-transport pathway inhibitors that affect the structure of the cytochrome (cyt) bc(1) complex to varying degrees, ranging from changes in hydroquinone (QH(2)) oxidation and cyt c(1) reduction kinetics to proteolytic accessibility of the hinge region of the iron-sulfur-containing subunit (Fe/S protein), have been reported. However, no instance has been documented of any ensuing change on the environment(s) of the [2Fe-2S] cluster. In this work, this issue was addressed in detail by taking advantage of the increased spectral and spatial resolution obtainable with orientation-dependent electron paramagnetic resonance (EPR) spectroscopic analysis of ordered membrane preparations. For the first time, perturbation of the low-potential electron-transport pathway by Q(i)-site inhibitors or various mutations was shown to change the EPR spectra of both the cyt b hemes and the [2Fe-2S] cluster of the Fe/S protein. In particular, two interlinked effects of Q;-site modifications on the Fe/S subunit, one changing the local environment of its [2Fe-2S] cluster and a second affecting the mobility of this subunit, are revealed. Remarkably, different inhibitors and mutations at or near the Q; site induce these two effects differently, indicating that the events occurring at the Q; site affect the global structure of the cyt bc(1). Furthermore, occupancy of discrete Q(i)-site subdomains differently impede the location of the Fe/S protein at the Q(o) site. These findings led us to propose that antimycin A and HQNO mimic the presence of QH(2) and Q at the Q(i) site, respectively. Implications of these findings in respect to the Q(o)-Q(i); sites communications and to multiple turnovers of the eyt bc, are discussed.