Proton-transfer pathways in the mitochondrial S. cerevisiae cytochrome c oxidase

Björck, M.L. and Vilhjámsdóttir, J. and Hartley, Andrew and Meunier, B. and Näsvik Öjemyr, L. and Marechal, Amandine and Brzezinski, P. (2019) Proton-transfer pathways in the mitochondrial S. cerevisiae cytochrome c oxidase. Scientific Reports 9 (1), p. 20207. ISSN 2045-2322.

Abstract

In cytochrome c oxidase (CytcO) reduction of O2 to water is linked to uptake of eight protons from the negative side of the membrane: four are substrate protons used to form water and four are pumped across the membrane. In bacterial oxidases, the substrate protons are taken up through the K and the D proton pathways, while the pumped protons are transferred through the D pathway. On the basis of studies with CytcO isolated from bovine heart mitochondria, it was suggested that in mitochondrial CytcOs the pumped protons are transferred though a third proton pathway, the H pathway, rather than through the D pathway. Here, we studied these reactions in S. cerevisiae CytcO, which serves as a model of the mammalian counterpart. We analyzed the effect of mutations in the D (Asn99Asp and Ile67Asn) and H pathways (Ser382Ala and Ser458Ala) and investigated the kinetics of electron and proton transfer during the reaction of the reduced CytcO with O2. No effects were observed with the H pathway variants while in the D pathway variants the functional effects were similar to those observed with the R. sphaeroides CytcO. The data indicate that the S. cerevisiae CytcO uses the D pathway for proton uptake and presumably also for proton pumping.

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