The polarity of proton translocation in some photosynthetic microorganisms.

Abstract

Observations on the direction of proton translocation coupled to photo-oxidoreduction and to respiration show that in chromatophores (or sonic particles) of Rhodospirillum rubrum and Rhodopseudomonas spheroides the direction is inwards, but in the intact organisms the direction is outwards. The relative proton translocation activities associated with photo-oxidoreduction and respiration appear to depend on the relative extent of development of the alternative pigment systems produced during growth. The direction of proton translocation associated with the oligomycin-sensitive ATPase activity in chromatophores of R. rubrum was the same as that associated with photo-oxidoreduction or respiration, suggesting that the proton current generated either by light or by respiration might alternatively drive ATP synthesis. Proton translocation, associated with photo-oxidoreduction or respiration, is directed outwards in intact Anabaena variabilis.