New perspectives on proton pumping in cellular respiration

Mårten Wikström, Vivek Sharma, Ville R I Kaila, Jonathan P. Hosler, Gerhard Hummer

    Research output: Contribution to journalReview Articlepeer-review

    139 Citations (Scopus)


    Complexes I, III (cytochrome bc1), and IV (cytochrome c oxidase) of the respiratory chain employ fundamentally different mechanisms for redox-coupled proton pumping. In the Q-cycle of cytochrome bc1, charge separation is the result of electron transfer through the membrane, whereas the protons are shuttled across the membrane by a neutral quinol carrier, QH2. In this Q cycle, the mobile quinols get protonated on the N-side of the membrane and deprotonated on the P-side. Cytochrome bc1 thus transduces chemical energy into an electrochemical gradient through a redox loop, but is not a true proton pump in the sense of moving protonic charge through the protein directly against a pmf. By contrast, cytochrome c oxidase, the terminal enzyme of the respiratory chain, operates as a true proton pump. In cytochrome c oxidase (CcO), the pathways of chemical electron and proton fluxes intersect in the binuclear center, and the pathway of pumped protons passes close to the BNC as well. This spatial proximity of proton and electron pathways establishes the tight electrostatic interactions one might expect for a redox-coupled proton pump.

    Original languageEnglish
    Pages (from-to)2196-2221
    Number of pages26
    JournalChemical Reviews
    Issue number5
    Publication statusPublished - 11 Mar 2015
    Publication typeA2 Review article in a scientific journal

    Publication forum classification

    • Publication forum level 2

    ASJC Scopus subject areas

    • General Chemistry


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