PMID: 216398Feb 8, 1979

Electrogenic events in the ubiquinone-cytochrome b/c2 oxidoreductase of Rhodopseudomonas sphaeroides

Biochimica Et Biophysica Acta
C L BashfordP L Dutton

Abstract

The reductant of ferricytochrome c2 in Rhodopseudomonas sphaeroides is a component, Z, which has an equilibrium oxidation-reduction reaction involving two electrons and two protons with a midpoint potential of 155 mV at pH 7. Under energy coupled conditions, the reduction of ferricytochrome c2 by ZH2 is obligatorily coupled to an apparently electrogenic reaction which is monitored by a red shift of the endogeneous carotenoids. Both ferricytochrome c2 reduction and the associated carotenoid bandshift are similarly affected by the concentrations of ZH2 and ferricytochrome c2, pH, temperature the inhibitors diphenylamine and antimycin, and the presence of ubiquinone. The second-order rate constant for ferricytochrome c2 reduction at pH 7.0 and at 24 degrees C was 2 - 10(9) M-1 - s-1, but this varied with pH, being 5.1 - 10(8) M-1 = s-1 at pH 5.2 and 4.3 - 10(9) M-1 - s-1 at pH 9.3. At pH 7 the reaction had an activation energy of 10.3 kcal/mol.

References

Citations

Mar 1, 2011·Biochimica Et Biophysica Acta·William A CramerEiki Yamashita
Mar 1, 1981·Bioscience Reports·C L Bashford
Jan 4, 2007·Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology·Armen Y Mulkidjanian
Jan 1, 1981·Membrane Biochemistry·C A BoicelliL Masotti

Related Concepts

Carotenoids
Cytochrome c Group
Cytochrome c Oxidase Subunit VIa
Cytochrome Reductases
Diphenylamine
Electrochemistry
Respiratory Chain
Multienzyme Complexes
NADH, NADPH Oxidoreductases
Oxidation-Reduction

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