NDLI: Proton uptake controls electron transfer in cytochrome c oxidase

Content Provider	PubMed Central
Author	Martin, Karpefors Ädelroth, Pia Zhen, Yuejun Ferguson-miller, Shelagh Brzezinski, Peter
Copyright Year	1998
Abstract	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 a 3–CuB before a proton is taken up, which assures a tight coupling of electron transfer to proton pumping.
Starting Page	13606
File Format	PDF
ISSN	10916490
e-ISSN	10916490
Journal	Proceedings of the National Academy of Sciences of the United States of America
Issue Number	23
Volume Number	95
Language	English
Publisher	The National Academy of Sciences
Publisher Date	1998-11-10
Access Restriction	Open
Rights Holder	The National Academy of Sciences
Subject Keyword	Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Multidisciplinary

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