Timing of electron and proton transfer in the ba3 cytochrome c oxidase from Thermus thermophilus

Christoph Von Ballmoos, Peter Lachmann, Robert B Gennis, Pia Ädelroth, Peter Brzezinski

Research output: Contribution to journalArticle

Abstract

Heme-copper oxidases are membrane-bound proteins that catalyze the reduction of O2 to H2O, a highly exergonic reaction. Part of the free energy of this reaction is used for pumping of protons across the membrane. The ba3 oxidase from Thermus thermophilus presumably uses a single proton pathway for the transfer of substrate protons used during O 2 reduction as well as for the transfer of the protons that are pumped across the membrane. The pumping stoichiometry (0.5 H+/ electron) is lower than that of most other (mitochondrial-like) oxidases characterized to date (1 H+/electron). We studied the pH dependence and deuterium isotope effect of the kinetics of electron and proton transfer reactions in the ba3 oxidase. The results from these studies suggest that the movement of protons to the catalytic site and movement to a site located some distance from the catalytic site [proposed to be a "proton-loading site" (PLS) for pumped protons] are separated in time, which allows individual investigation of these reactions. A scenario in which the uptake and release of a pumped proton occurs upon every second transfer of an electron to the catalytic site would explain the decreased proton pumping stoichiometry compared to that of mitochondrial-like oxidases. (Graph Presented).

Original languageEnglish (US)
Pages (from-to)4507-4517
Number of pages11
JournalBiochemistry
Volume51
Issue number22
DOIs
StatePublished - Jun 5 2012

ASJC Scopus subject areas

  • Biochemistry

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