Comparative Kinetics of Q1 Site Inhibitors of Cytochrome bc1 Complex: Picomolar Antimycin and Micromolar Cyazofamid
Comparative Kinetics of Q1 Site Inhibitors of Cytochrome bc1 Complex: Picomolar Antimycin and Micromolar Cyazofamid
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DOI：
10.1111/cbdd.12199
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发表时间：
2014-01-01
影响因子：
3
通讯作者：
Yang, Guang-Fu
中科院分区：
文献类型：
--
作者：
Li, Hui;Zhu, Xiao-Lei;Yang, Guang-Fu
抗霉素和氰霜唑是线粒体呼吸链的特异性抑制剂，与细胞色素bc（1）复合物的Q（i）位点结合。为了了解Q（i）抑制剂的详细分子抑制机制，我们对它们对猪bc（1）复合物的抑制动力学进行了比较研究。结果表明，安替霉素对琥珀酸-细胞色素c还原酶（SCR）是一种缓慢的紧结合抑制剂，Ki =0.033 ± 0.00027nm，对细胞色素c为非竞争性抑制。氰霜唑是SCR的经典抑制剂，Ki =12.90 +/- 0.91m，并且是相对于细胞色素c的非竞争性抑制剂。它们对底物DBH 2均表现出竞争性抑制作用。进行了进一步的分子对接和量子力学计算。结果表明，抗霉素在结合过程中发生了明显的构象变化。晶体中构象与结合袋中构象之间的能垒近似为13.63kcal/mol。抗霉素与Asp 228形成氢键，与Lys 227和His 201形成两个水桥氢键，而氰霜唑仅与Asp 228形成一个氢键。构象变化和不同的氢键网络可能解释了为什么抗霉素是一个缓慢的紧密结合抑制剂，而氰霜唑是一个经典的抑制剂。
Antimycin and cyazofamid are specific inhibitors of the mitochondrial respiratory chain and bind to the Q(i) site of the cytochrome bc(1) complex. With the aim to understand the detailed molecular inhibition mechanism of Q(i) inhibitors, we performed a comparative investigation of the inhibitory kinetics of them against the porcine bc(1) complex. The results showed that antimycin is a slow tight-binding inhibitor of succinate-cytochrome c reductase (SCR) with K-i=0.033 +/- 0.00027nm and non-competitive inhibition with respect to cytochrome c. Cyazofamid is a classical inhibitor of SCR with K-i=12.90 +/- 0.91m and a non-competitive inhibitor with respect to cytochrome c. Both of them show competitive inhibition with respect to substrate DBH2. Further molecular docking and quantum mechanics calculations were performed. The results showed that antimycin underwent significant conformational change upon the binding. The energy barrier between the conformations in the crystal and in the binding pocket is similar to 13.63kcal/mol. Antimycin formed an H-bond with Asp228 and two water-bridged H-bonds with Lys227 and His201, whereas cyazofamid formed only one H-bond with Asp228. The conformational change and the different hydrogen bonding network might account for why antimycin is a slow tight-binding inhibitor, whereas cyazofamid is a classic inhibitor.