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

• 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 throughthe 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 withO2. 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 pumping.

Ämnesord

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Nyckelord

cytochrome c oxidase

electron transfer

cytochrome aa3

membrane protein

ligand

kinetics

mechanism

Biochemistry

biokemi

Publikations- och innehållstyp

vet (ämneskategori)

ovr (ämneskategori)