A common coupling mechanism for A-type heme-copper oxidases from bacteria to mitochondria

Marechal, Amandine and Xu, J.-Y. and Genko, N. and Hartley, Andrew and Haraux, F. and Meunier, B. and Rich, P. (2020) A common coupling mechanism for A-type heme-copper oxidases from bacteria to mitochondria. Proceedings of the National Academy of Sciences of the United States of America 117 (17), pp. 9349-9355. ISSN 0027-8424.

Abstract

Mitochondria metabolise almost all of the oxygen that we consume, reducing it to water by cytochrome c oxidase (CcO). CcO maximises energy capture into the protonmotive force by pumping protons across the mitochondrial inner membrane. Forty years after the H+/e- stoichiometry was established, a consensus has yet to be reached on the route taken by pumped protons to traverse CcO’s hydrophobic core and on whether bacterial and mitochondrial CcOs operate via the same coupling mechanism. To resolve this, we exploited the unique amenability to mitochondrial DNA mutagenesis of the yeast S. cerevisiae to introduce single point mutations in the hydrophilic pathways of CcO to test function. From ADP/O ratio measurements on preparations of intact mitochondria, we definitely established that the D-channel, and not the H-channel, is the proton pump of the yeast mitochondrial enzyme, supporting an identical coupling mechanism in all forms of the enzyme.

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