Chemiosmotic coupling in cytochrome oxidase

Mitchell, Peter; Mitchell, Roy; Moody, A. John; West, Ian; Baum, Harold; Wrigglesworth, John M.

doi:10.1016/0014-5793(85)80863-2

Cited by 83 publications

(17 citation statements)

References 39 publications

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“…It would be interesting to verify whether there is a direct relationship in various oxidases between the display of peroxidase activity and redox-linked proton ejection. The observed variability in the H'/e-ratio would seem, in principle, to favour indirect co-operative coupling models [2, 4, 271 instead of direct models [25]. It is, however, also possible that mechanisms like gating of electron transfer through coupled and uncoupled pathways [67,681 or transition of the oxidase from a monomeric uncoupled condition to dimeric coupled state [26, 601 may result in a variable stoichiometry of proton translocation, this taking place either by direct of indirect mechanism.…”

Section: Discussionmentioning

confidence: 99%

“…1 A. The reducing equivalents added were 4 pM ferrocytochrome c. Mg2' in/out refers to Mg'+-containing vesicles prepared according to [48]. Respiration was measured polarographically in 40 mM KCl, 10 mM Hepes pH 7.4, 0.1 mM EDTA, 25 mM ascorbate, 50 pM cytochrome c and 0.03 pM cytochrome oxidase vesicles. State 111 was induced by the addition of valinomycin (1 pg/ml) and 3 pM CCP.…”

Section: + On Redox-linked Proton Translocation Respiratory Control mentioning

confidence: 99%

“…On the other hand, Mitchell et al [25] have now developed a direct coupled mechanism based on hydrogen conduction by oxygen across the osmotic barrier of the membrane. This mechanism is, indeed, derived from a model proposed by Baum and Wrigglesworth [28], according to which the H f / e -stoichiometry for proton pumping in the oxidase would be 0.5.…”

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confidence: 99%

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Characteristics of the redox‐linked proton ejection in beef‐heart cytochrome c oxidase reconstituted in liposomes

Papa

Capitanio

Nitto

1987

European Journal of Biochemistry

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In this paper a study is presented of the characteristics of redox‐linked proton ejection exhibited by isolated beef‐heart cytochrome c oxidase incorporated in asolectin vesicles. The enzyme was 90% oriented ‘right‐side out’ as in the mitochondrial membrane. The effects on the H+/e− stoichiometry of the modalities of activation of electron flow, the pH of the medium and its ionic composition were investigated. The results obtained show that, whilst ferrocytochrome c pulses of the aerobic oxidase vesicles at neutral pH and in the presence of saturating concentrations of valinomycin and K+ to ensure charge compensation produced H+/e− ratios around 1 (as has been shown previously), oxygen pulses of reduced anaerobic vesicles supplemented with cytochrome c, gave H+/e− ratios around 0.3. The H+/e− ratios exhibited, with both reductant and oxidant pulses, a marked pH dependence. Maximum values were observed at pH 7.0–7.7, which decreased to negligible values at acidic pH with apparent pKa of 6.7–6.3. Mg2+ and Ca2+ caused a marked depression of the H+/e− ratio, which in the presence of these cations and after a few ferrocytochrome pulses, became negligible. Analysis of cytochrome c oxidation showed that the modalities of activation of electron flow and divalent cations exerted profound effects on the kinetics of cytochrome c oxidation by oxidase vesicles. The observations presented seem to provide interesting clues for the nature and mechanism of redox‐linked proton ejection in reconstituted cytochrome c oxidase.

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Section: Discussionmentioning

confidence: 99%

Section: + On Redox-linked Proton Translocation Respiratory Control mentioning

confidence: 99%

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Characteristics of the redox‐linked proton ejection in beef‐heart cytochrome c oxidase reconstituted in liposomes

Papa

Capitanio

Nitto

1987

European Journal of Biochemistry

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“…Formally, this could be interpreted as H,02 binding COX in a fully protonated state (e.g. [9,19]): (4) Volume 3 12, number 1…”

Section: Proronarion Seem Of the Contpourrd Pmentioning

confidence: 99%

pH changes associated with cytochrome c oxidase reaction with H₂O₂ Protonation state of the peroxy and oxoferryl intermediates

et al. 1992

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pH changes associated with the mitochondrial cytochrome oxidase reaction with H2O2 have been studied. In the presence of forricyanide or Tris‐phenanthroline complex of CoIII as electron acceptors, reaction or H2O2 with the oxidized cytochrome oxidase is accompanied by a steady proton release with a rate constant of ca. 3 M−1 s−1 at pH 6.8. The acidification is completely inhibited by superoxide dismutase and its pro‐steady‐state kinetics correlates with that of the oxoferryl compound (F) accumulation. Apparently, the proton release is linked to superoxide generation by cytochrome oxidase under these conditions. In the presence of superoxide dismutase and without the electron acceptors, the H2O2‐induced transitions of cytochrome oxidase from the oxidized to the peroxy (P) and from the peroxy to the oxoferryl state are not associated with any significant proton release or uptake. The results point to the following mechanism of O− 2 generation and protonation states of the cytochrome oxidase compounds P and F:

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“…CUA [2,3], haem aA [4] (nomenclature of [5]), and the binuclear centre [3,6,7] have all been invoked as possible participants, in a range of direct [8] and indirect [9,10] chemiosmotic mechanisms [l 1].…”

Section: Introductionmentioning

confidence: 99%

The location of Cu_A in mammalian cytochrome c oxidase

1988

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Imposition of a protonmotive force across the inner membrane of coupled cyanide-inhibited, beef heart mitochondria by addition of ATP causes reduction of cytochrome c and Cu^ with concomitant oxidation of haem aA. The data are consistent with previous demonstrations of an intramembrane location of haem a^ but further indicate that CUA is very close to the cytosolic surface of the membrane. The implications of this finding for electron transfer route and the site of the proton pumping chemistry are discussed.

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Chemiosmotic coupling in cytochrome oxidase

Cited by 83 publications

References 39 publications

Characteristics of the redox‐linked proton ejection in beef‐heart cytochrome c oxidase reconstituted in liposomes

Characteristics of the redox‐linked proton ejection in beef‐heart cytochrome c oxidase reconstituted in liposomes

pH changes associated with cytochrome c oxidase reaction with H₂O₂ Protonation state of the peroxy and oxoferryl intermediates

The location of Cu_A in mammalian cytochrome c oxidase

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Chemiosmotic coupling in cytochrome oxidase

Cited by 83 publications

References 39 publications

Characteristics of the redox‐linked proton ejection in beef‐heart cytochrome c oxidase reconstituted in liposomes

Characteristics of the redox‐linked proton ejection in beef‐heart cytochrome c oxidase reconstituted in liposomes

pH changes associated with cytochrome c oxidase reaction with H2O2 Protonation state of the peroxy and oxoferryl intermediates

The location of CuA in mammalian cytochrome c oxidase

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pH changes associated with cytochrome c oxidase reaction with H₂O₂ Protonation state of the peroxy and oxoferryl intermediates

The location of Cu_A in mammalian cytochrome c oxidase