Identification of the electron transfers in cytochrome oxidase that are coupled to proton-pumping (original) (raw)

Nature volume 338, pages 776–778 (1989) Cite this article

Abstract

MITOCHONDRIAL cytochrome oxidase is a functionally complex, membrane-bound respiratory enzyme which catalyses both the reduction of O2 to water and proton-pumping. During respiration, an exogenous donor, cytochrome_c_, donates four electrons to O2 bound at the bimetallic haem _a_3 Fe–Cu centre within the enzyme. These four electron transfers are mediated by the enzyme's haem a and CuA redox centres and result in the translocation of four protons across the inner mitochondria! membrane.1 The molecular mechanism of proton translocation has not yet been delineated, however, and in the absence of direct experimental evidence all four electron transfers have been assumed to couple equally to proton-pumping. Here, I report the effects of proton-motive force and membrane potential on two equilibria involving intermediates of the bimetallic centre at different levels of O2 reduction.2–7 The results show that only two of the electron transfers, to the 'peroxy' and 'oxyferryl' intermediates of the bimetallic centre, are linked to proton translocation, a finding which strongly constrains candidate mechanisms for proton-pumping.

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Authors and Affiliations

  1. Department of Medical Chemistry, University of Helsinki, Siltavuorenpenger 10A, SF-00170, Helsinki, Finland
    Mårten Wikström

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Wikström, M. Identification of the electron transfers in cytochrome oxidase that are coupled to proton-pumping.Nature 338, 776–778 (1989). https://doi.org/10.1038/338776a0

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