Partial reversion of the electrogenic reaction in the ubiquinol: cytochrome c2-oxidoreductase of Rhodobacter sphaeroides chromatophores under neutral and alkaline conditions.
The interaction of the photosynthetic reaction center (RC)-generated ubiquinol with the ubiquinone-reducing center C of ubiquinol:cytochrome c2-oxidoreductase (bc1-complex) has been studied electrometrically in Rhodobacter sphaeroides chromatophores. The addition of myxothiazol inhibited the ubiquinol-oxidizing center Z, suppressing the phases of membrane potential generation by the bc1-complex, but at the same time induced an electrogenic phase of opposite polarity, sensitive to antimycin A, the inhibitor of center C. The rise time of this reverse phase varied from 3 ms at pH 6.0 to 1 ms at pH 9.5. At pH greater than 9.5 the reverse phase was limited by the rate of ubiquinol formation in RC. The magnitude of the reverse phase was constant within the pH range 7.5-10.0. It is assumed that the reverse phase is due to the electrogenic deprotonation reaction which takes place after the binding of the RC-generated ubiquinol to center C.
Mulkidjanian AYa
A.N. Belozersky Laboratory of Molecular Biology and Bioorganic Chemistry, Department of Biology, Moscow State University, USSR.
Mamedov
M D
MD
Semenov AYu
Shinkarev
V P
VP
Verkhovsky
M I
MI
Drachev
L A
LA
D003574:Cytochrome c Group / Q000378:metabolism; D045362:Cytochromes c2; D014450:Electron Transport Complex III / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials; D008689:Methacrylates; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D012242:Rhodobacter sphaeroides / Q000201:enzymology*; D013844:Thiazoles / Q000494:pharmacology; D014451:Ubiquinone / Q000378:metabolism* / Q000031:analogs & derivatives
D003574:Cytochrome c Group; D008689:Methacrylates; D045322:Photosynthetic Reaction Center Complex Proteins; D013844:Thiazoles; D014451:Ubiquinone; C030517:myxothiazol; D045362:Cytochromes c2; D014450:Electron Transport Complex III; C003741:ubiquinol