Mulkidjanian AYa, Mamedov MD, Semenov AYu, Shinkarev VP, Verkhovsky MI, Drachev LA. Partial reversion of the electrogenic reaction in the ubiquinol: cytochrome c2-oxidoreductase of Rhodobacter sphaeroides chromatophores under neutral and alkaline conditions.
FEBS Lett 1990;
277:127-30. [PMID:
2176609 DOI:
10.1016/0014-5793(90)80825-4]
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Abstract
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.
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