[Effect of deuteration on the gramicidin-sensitive electron-transport reactions in chloroplasts].

The uncoupling effects of gramicidine and NH4Cl on the light-induced electron transport were studied in isolated pea chloroplasts placed in H2O- or D2O-media. Gramicidine at 10(-6) M had no uncoupling effect on the rate of ferricyanide-supported O2 evolution in a D2O-medium, but enhanced the ferricyanide reduction in a H2O-medium and completely inhibited the light-induced alkalinization both in H2O- and D2O-suspended chloroplasts. The rate of electron transport with methylviologen as an acceptor was gramicidine-sensitive (uncoupling) both in preparations with H2O and D2O. In D2O-suspended chloroplasts the phosphorylation activity was retained as well as control of ferricyanide-dependent electron flow by ADP--phosphate and NH4Cl. It was assumed that some electron carriers on the inner surface of thylakoid membranes become inaccessible to ferricyanide upon deuteration.