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• 作者：Jeffrey Havens ; Michela Castellani ; Thomas Kleinschroth ; Bernd Ludwig ; Bill Durham ; Francis Millett
• 刊名：Biochemistry
• 出版年：2011
• 出版时间：December 6, 2011
• 年：2011
• 卷：50
• 期：48
• 页码：10462-10472
• 全文大小：386K
• 年卷期：v.50,no.48(December 6, 2011)
• ISSN：1520-4995

文摘

Domain rotation of the Rieske iron鈥搒ulfur protein (ISP) between the cytochrome (cyt) b and cyt c₁ redox centers plays a key role in the mechanism of the cyt bc₁ complex. Electron transfer within the cyt bc₁ complex of Paracoccus denitrificans was studied using a ruthenium dimer to rapidly photo-oxidize cyt c₁ within 1 渭s and initiate the reaction. In the absence of any added quinol or inhibitor of the bc₁ complex at pH 8.0, electron transfer from reduced ISP to cyt c₁ was biphasic with rate constants of k_1f = 6300 卤 3000 s^鈥?and k_1s = 640 卤 300 s^鈥? and amplitudes of 10 卤 3% and 16 卤 4% of the total amount of cyt c₁ photooxidized. Upon addition of any of the P_m type inhibitors MOA-stilbene, myxothiazol, or azoxystrobin to cyt bc₁ in the absence of quinol, the total amplitude increased 2-fold, consistent with a decrease in redox potential of the ISP. In addition, the relative amplitude of the fast phase increased significantly, consistent with a change in the dynamics of the ISP domain rotation. In contrast, addition of the P_f type inhibitors JG-144 and famoxadone decreased the rate constant k_1f by 5鈥?0-fold and increased the amplitude over 2-fold. Addition of quinol substrate in the absence of inhibitors led to a 2-fold increase in the amplitude of the k_1f phase. The effect of QH₂ on the kinetics of electron transfer from reduced ISP to cyt c₁ was thus similar to that of the P_m inhibitors and very different from that of the P_f inhibitors. The current results indicate that the species occupying the Q_o site has a significant conformational influence on the dynamics of the ISP domain rotation.