Structural Changes and Proton Transfer in Cytochrome  c  Oxidase

Vilhjálmsdóttir, Jóhanna; Johansson, Anders; Brzezinski, Peter

doi:10.1016/j.bbabio.2016.04.320

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“…The current models of proton pumping in CcO are essentially of two types: one, mainly based on work on bovine CcO in which the low‐spin heme a is the key element of the pump (Babcock & Callahan, ; Rousseau et al ., ; Papa, Capitanio & Villani, ; Yoshikawa et al ., ; Tsukihara et al ., ), the other based on work on bacterial CcO, in which the key role is played by the binuclear heme a 3 –Cu B centre (Brzezinski, ; Kaila, Verkhovsky & Wikström, ; VilhJalmsdottir, Johansson & Brzezinski, ). As discussed below, allosteric cooperativity of the redox chemistry at the low‐spin heme a and the heme a 3 –Cu B centre can, however, both contribute to the proton‐pumping activity of CcO.…”

Section: Cytochrome C Oxidasementioning

confidence: 99%

The mechanism of coupling between oxido‐reduction and proton translocation in respiratory chain enzymes

2017

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The respiratory chain of mitochondria and bacteria is made up of a set of membrane-associated enzyme complexes which catalyse sequential, stepwise transfer of reducing equivalents from substrates to oxygen and convert redox energy into a transmembrane protonmotive force (PMF) by proton translocation from a negative (N) to a positive (P) aqueous phase separated by the coupling membrane. There are three basic mechanisms by which a membrane-associated redox enzyme can generate a PMF. These are membrane anisotropic arrangement of the primary redox catalysis with: (i) vectorial electron transfer by redox metal centres from the P to the N side of the membrane; (ii) hydrogen transfer by movement of quinones across the membrane, from a reduction site at the N side to an oxidation site at the P side; (iii) a different type of mechanism based on co-operative allosteric linkage between electron transfer at the metal redox centres and transmembrane electrogenic proton translocation by apoproteins.The results of advanced experimental and theoretical analyses and in particular X-ray crystallography show that these three mechanisms contribute differently to the protonmotive activity of cytochrome c oxidase, ubiquinone-cytochrome c oxidoreductase and NADH-ubiquinone oxidoreductase of the respiratory chain.This review considers the main features, recent experimental advances and still unresolved problems in the molecular/atomic mechanism of coupling between the transfer of reducing equivalents and proton translocation in these three protonmotive redox complexes.

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