The Inside pH Determines Rates of Electron and Proton Transfer in Vesicle-Reconstituted Cytochrome c Oxidase
2007 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1767, no 5, 381-386 p.Article in journal (Refereed) Published
Cytochrome c oxidase is the terminal enzyme in the respiratory chains of mitochondria and many bacteria where it translocates protons across a membrane thereby maintaining an electrochemical proton gradient. Results from earlier studies on detergent-solubilized cytochrome c oxidase have shown that individual reaction steps associated with proton pumping display pH-dependent kinetics. Here, we investigated the effect of pH on the kinetics of these reaction steps with membrane-reconstituted cytochrome c oxidase such that the pH was adjusted to different values on the inside and outside of the membrane. The results show that the pH on the inside of the membrane fully determines the kinetics of internal electron transfers that are linked to proton pumping. Thus, even though proton release is rate limiting for these reaction steps (Salomonsson et al., Proc. Natl. Acad. Sci. USA, 2005, 102, 17624), the transition kinetics is insensitive to the outside pH (in the range 6–9.5).
Place, publisher, year, edition, pages
2007. Vol. 1767, no 5, 381-386 p.
Rhodobacter sphaeroides; Proton pumping; Cytochrome aa3; Respiration; Kinetics
Biochemistry and Molecular Biology
IdentifiersURN: urn:nbn:se:su:diva-24244DOI: 10.1016/j.bbabio.2007.02.023OAI: oai:DiVA.org:su-24244DiVA: diva2:197086
Part of urn:nbn:se:su:diva-68062007-05-042007-04-262010-07-29Bibliographically approved