[Cyclic electron transfer and membrane potential generation in chromatophores on non-sulfur bacteria Rhodospirillum rubrum]

The uptake of permeant anions by cells and chromatophores of the non-sulfur purple bacteria R. rubrum has been studied. Antimycin A causes biphasic inhibition of the light-induced uptake of tetraphenylborate anions (TB-) by the cells and the isolated chromatophores incubated under anaerobic conditions. The first phase is observed at small concentrations of antimycin and is due to its effect as an inhibitor of the cyclic electron transfer. The second phase is observed at concentrations higher than 1 microM and is due to its effect as an uncoupler of photophosphorylation. The inhibitory effect of antimycin is greatly enhanced under aerobic conditions and is due to its effect as an uncoupler of photophosphorylation. The innic cyclic redox chain in the isolated and intracellular chromatophores is apparently operated in two regimens: 1) as a chain including all redox components and, 2) as a chain functioning without cytochromes of the b type.