Modulation of the electron redistribution in mixed valence cytochrome c oxidase by protein conformational changes
Modulation of the electron redistribution in mixed valence cytochrome c oxidase by protein conformational changes
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DOI：
10.1074/jbc.m310729200
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发表时间：
2004-03-05
影响因子：
4.8
通讯作者：
Rousseau, DL
中科院分区：
文献类型：
--
作者：
Ji, H;Yeh, SR;Rousseau, DL
用共振拉曼光谱研究了CO与CO结合的混合价态光解后，细胞色素c氧化酶四个氧化还原中心的两个电子的重新分配。为了解释从5ms到2ms的动力学数据和平衡结果，提出了一个模型，其中电子再分配是由蛋白质构象在超过2ms的时间窗口内从新生的P-1状态转变到松弛的P-2状态来调节的。在该模型中，考虑了所有六种可能的双电子还原态。血红素a(3)的光谱受到Cu-B的氧化还原状态的干扰，这导致血红素a(3)具有一个电子还原双核中心的物种的高种群数量，导致双核中心有零电子或两个电子的氧化还原物种的四个标准光谱在拟合动力学数据时存在显著的残差。在平衡条件下，P-2态的构象变化使双核中心只有一个电子的氧化还原态相对于有零或两个电子的氧化还原态不稳定。结果，氧化还原平衡被打乱，电子被重新分配。电子再分布受蛋白质构象调节的新动力学方案的模拟结果与平衡和动力学数据吻合较好，证明了该模型的有效性。
The redistribution of two electrons in the four redox centers of cytochrome c oxidase following photodissociation of CO from the CO-bound mixed valence species has been examined by resonance Raman spectroscopy. To account for both the kinetic data, obtained from 5 mus to 2 ms, and the equilibrium results, a model is proposed in which the electron redistribution is modulated by a protein conformation transition from a nascent P-1 state to a relaxed P-2 state in a time window longer than 2 ms. In this model, all six possible two-electron reduced species are considered. The high population of species with a one-electron reduced binuclear center, in which the spectrum of heme a(3) is perturbed by the redox state of Cu-B, accounts for the significant residuals in the fitting of the kinetic data with four standard spectra derived from redox species with either zero or two electrons in the binuclear center. Under equilibrium conditions, the conformational change to the P-2 state destabilizes the redox states with only one electron in the binuclear center with respect to those with either zero or two electrons. As a result, the redox equilibrium is perturbed, and the electrons are redistributed. A simulation based on the new kinetics scheme, in which the electron redistribution is modulated by the protein conformation, gives reasonable agreement with both the equilibrium and the kinetic data, demonstrating the validity of this model.