文章基本信息

标题：Proton uptake controls electron transfer in cytochrome c oxidase
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作者：Martin Karpefors ; Pia Ädelroth ; Yuejun Zhen 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1998
卷号：95
期号：23
页码：13606-13611
DOI：10.1073/pnas.95.23.13606
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：In cytochrome c oxidase, a requirement for proton pumping is a tight coupling between electron and proton transfer, which could be accomplished if internal electron-transfer rates were controlled by uptake of protons. During reaction of the fully reduced enzyme with oxygen, concomitant with the "peroxy" to "oxoferryl" transition, internal transfer of the fourth electron from CuA to heme a has the same rate as proton uptake from the bulk solution (8,000 s-1). The question was therefore raised whether the proton uptake controls electron transfer or vice versa. To resolve this question, we have studied a site-specific mutant of the Rhodobacter sphaeroides enzyme in which methionine 263 (SU II), a CuA ligand, was replaced by leucine, which resulted in an increased redox potential of CuA. During reaction of the reduced mutant enzyme with O2, a proton was taken up at the same rate as in the wild-type enzyme (8,000 s-1), whereas electron transfer from CuA to heme a was impaired. Together with results from studies of the EQ(I-286) mutant enzyme, in which both proton uptake and electron transfer from CuA to heme a were blocked, the results from this study show that the CuA [->] heme a electron transfer is controlled by the proton uptake and not vice versa. This mechanism prevents further electron transfer to heme a3-CuB before a proton is taken up, which assures a tight coupling of electron transfer to proton pumping.
关键词：flow–flash/proton pumping/cytochrome aa ₃/flash photolysis/gating