PMID: 202311Dec 23, 1977

Single and multiple turnover reactions in the ubiquinone-cytochrome b-c2 oxidoreductase of Rhodopseudomonas sphaeroids: the physical chemistry of the major electron donor to cytochrome c2, and its coupled reactions

Biochimica Et Biophysica Acta
R C Prince, P L Dutton

Abstract

We have examined the thermodynamic properties of the physiological electron donor to ferricytochrome c2 in chromatophores from the photosynthetic bacterium Rhodopseudomonas sphaeroides. This donor (Z), which is capable of reducing the ferricytochrome with a halftime of 1-2 ms under optimal conditions, has an oxidation-reduction midpoint potential of close to 150 mV at pH 7.0, and apparently requires two electrons and two protons for its equilibrium reduction. The state of reduction of Z, which may be a quinone.protein complex near the inner (cytochrome c2) side of the membrane, appears to govern the rate at which the cyclic photosynthetic electron transport system can operate. If Z is oxidized prior to the flash-oxidation of cytochrome c2, the re-reduction of the cytochrome takes hundreds of milliseconds and no third phase of the carotenoid bandshift occurs. In contrast if Z is reduced before flash activation, the cytochrome is rereduced within milliseconds and the third phase of the carotenoid bandshift occurs. The prior reduction of Z also has a dramatic effect on the uncoupler sensitivity of the rate of electron flow; if it is oxidized prior to activation, uncoupler can stimulate the cytochrome rereduction after several turn...Continue Reading

References

Oct 31, 1974·Biochimica Et Biophysica Acta·P L Dutton, D F Wilson
Mar 1, 1967·Proceedings of the National Academy of Sciences of the United States of America·H BaumS H Lipton

Citations

Jan 1, 1989·Photosynthesis Research·A R Crofts, Z Wang
Aug 1, 1978·Journal of Bioenergetics and Biomembranes·A B Melandri, D Zannoni
Aug 1, 1983·Journal of Bioenergetics and Biomembranes·A V Oleskin, V D Samuilov
Nov 1, 1980·Proceedings of the National Academy of Sciences of the United States of America·N K PackhamP L Dutton
Oct 1, 1985·Journal of Bioenergetics and Biomembranes·P PasqualiG Lenaz
Apr 8, 2006·Biochimica Et Biophysica Acta·A R CroftsStuart Rose
Jan 4, 2007·Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology·Armen Y Mulkidjanian

Related Concepts

Carotenoids
Cytochrome c Group
Cytochrome Reductases
Electrochemistry
Respiratory Chain
Light
Oxidation-Reduction
Rhodobacter sphaeroides
Spectrophotometry
Ubiquinone

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