The Metals of Cytochrome C Oxidase and their Role in the Kinetics of Electron Transfer and Proton Pumping

AbstractIn 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 through the 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 with O2. 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 presumably also for proton pumping.

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Kinetics of proton pumping in cytochrome c oxidase

The Journal of Chemical Physics ◽

10.1063/1.3155213 ◽

2009 ◽

Vol 130 (23) ◽

pp. 235105 ◽

Cited By ~ 13

Author(s):

Anatoly Yu. Smirnov ◽

Lev G. Mourokh ◽

Franco Nori

Keyword(s):

Cytochrome C ◽

Cytochrome C Oxidase ◽

Proton Pumping ◽

Kinetics Of

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Ionic strength dependence of the kinetics of electron transfer from bovine mitochondrial cytochrome c to bovine cytochrome c oxidase

Biochemistry ◽

10.1021/bi00215a031 ◽

1991 ◽

Vol 30 (1) ◽

pp. 213-222 ◽

Cited By ~ 64

Author(s):

James T. Hazzard ◽

Shou Yu Rong ◽

Gordon Tollin

Keyword(s):

Electron Transfer ◽

Ionic Strength ◽

Cytochrome C ◽

Cytochrome C Oxidase ◽

Mitochondrial Cytochrome ◽

Ionic Strength Dependence ◽

Strength Dependence ◽

Kinetics Of ◽

Mitochondrial Cytochrome C

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Molecular architecture of the proton diode of cytochrome c oxidase

Biochemical Society Transactions ◽

10.1042/bst0361169 ◽

2008 ◽

Vol 36 (6) ◽

pp. 1169-1174 ◽

Cited By ~ 9

Author(s):

Peter Brzezinski ◽

Joachim Reimann ◽

Pia Ädelroth

Keyword(s):

Electron Transfer ◽

Cytochrome C ◽

Proton Transfer ◽

Cytochrome C Oxidase ◽

Proton Translocation ◽

Short Review ◽

Proton Pumping ◽

Molecular Architecture ◽

Electrochemical Gradient ◽

Membrane Bound

CytcO (cytochrome c oxidase) is a membrane-bound multisubunit protein which catalyses the reduction of O2 to H2O. The reaction is arranged topographically so that the electrons and protons are taken from opposite sides of the membrane and, in addition, it is also linked to proton pumping across the membrane. Thus the CytcO moves an equivalent of two positive charges across the membrane per electron transferred to O2. Proton transfer through CytcO must be controlled by the protein to prevent leaks, which would dissipate the proton electrochemical gradient that is maintained across the membrane. The molecular mechanism by which the protein controls the unidirectionality of proton-transfer (cf. proton diode) reactions and energetically links electron transfer to proton translocation is not known. This short review summarizes selected results from studies aimed at understanding this mechanism, and we discuss a possible mechanistic principle utilized by the oxidase to pump protons.

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