Electrogenic reduction of the secondary quinone acceptor in chromatophores of Rhodospirillum rubrum: Rapid kinetics measurements

Electron transfer Q A → Q B has been reconstituted with added Q-10 in Rhodospirillum rubrum chromatophores associated with a phospholipid-impregnated collodion film. Rapid kinetics measurements of laser flash-induced ΔΨ generated in the chromatophores show that whereas electron transfer from Q a − to Q B upon the first flash is not electrogenic in dark-adapted chromatophores, reduction of Q − B to Q bh 2 induced by the second flash gives rise to an electrogenic phase with τ = 250 μs at pH 7.5 which contributes about 10% to the total ΔΨ generated upon the flash. The electrogenic phase is ascribed to vectorial protonation of Q 2− B.