Role of the conserved arginine pair in proton and electron transfer in cytochrome c oxidase
Role of the conserved arginine pair in proton and electron transfer in cytochrome c oxidase
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DOI：
10.1021/bi036279o
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发表时间：
2004-05-18
期刊：
影响因子：
2.9
通讯作者：
Ferguson-Miller, S
中科院分区：
文献类型：
--
作者：
Qian, J;Mills, DA;Ferguson-Miller, S
在细胞色素氧化酶的所有高分辨率晶体结构中，在血红素上方观察到氢键网络。它包括水和一对能直接与血红素a和血红素a（3）丙酸盐相互作用的二聚体R481和R482（Rhodobacter sphaeroides编号）。氢键网络为质子释放提供了潜在的途径。也已经提出了三聚氰胺和它们之间的骨架肽键形成Cu-A和血红素a之间的易化电子转移途径的一部分。我们的研究表明，R482（K，Q和A）和R481（K）的突变保留了大量的活性，并能够泵质子，但在一定程度上降低了速率和化学计量。从细胞色素C到Cu-A的电子转移速率减慢表明除了R到K突变体之外，所有突变体中细胞色素C结合的方向都发生了变化。突变体R482 P在其结构上更受干扰，并且在血红素a和Cu-A之间的氧化还原电位差上改变：R482 P为+18 mV，野生型为+46 mV（血红素a-Cu-A）。Cu-A和血红素a之间的电子转移速率也从野生型的93000 s（-1）改变到氧化R482P突变体的50 s（-1），这让人想起在Cu-A配体突变体H260 N中观察到的变化。在这两种情况下，都不是由氧化还原电位改变引起的速率的2000倍的变化，这表明两者都引起了电子转移路径或重组能量的重大改变。
A hydrogen-bonded network is observed above the hemes in all of the high-resolution crystal structures of cytochrome oxidases. It includes water and a pair of arginines, R481 and R482 (Rhodobacter sphaeroides numbering), that interact directly with heme a and the heme a(3) propionates. The hydrogen-bonded network provides potential pathways for proton release. The arginines, and the backbone peptide bond between them, have also been proposed to form part of a facilitated electron transfer route between Cu-A and heme a. Our studies show that mutations of R482 (K, Q, and A) and R481 (K) retain substantial activity and are able to pump protons, but at somewhat reduced rates and stoichiometries. A slowed rate of electron transfer from cytochrome C to Cu-A Suggests a change in the orientation of cytochrome c binding in all but the R to K mutants. The mutant R482P is more perturbed in its structure and is altered in the redox potential difference between heme a and Cu-A: + 18 mV for R482P and +46 mV for the wild type (heme a - Cu-A). The electron transfer rate between Cu-A and heme a is also altered from 93000 s(-1) in the wild type to 50 s(-1) in the oxidized R482P mutant, reminiscent of changes observed in a Cu-A-ligand mutant, H260N. In neither case is the similar to2000-fold change in the rate accounted for by the altered redox potentials, suggesting that both cause a major modification in the path or reorganization energy of electron transfer.