ATP SYNTHASE - DRIVEN AND ACTIVATED BY PROTONMOTIVE FORCE

ATP synthase (F-ATPase) of chloroplasts, CF0CF1, is both activated and driven by transmembrane protonmotive force. We dichotomized between a ctivating and driving proton transfer by specific inhibitors, tentoxin and venturicidin. Thylakoid membranes were submitted to voltage steps (by flashing fight) that were superimposed to a steady pH-difference. Transient proton uptake, transfer and release by CF0CF1 were studied by spectroscopic probes. Both, activation and catalysis required all t hree partial reactions of the proton. A fast electrogenic reaction pre ceded the catalytic turnover of CF0CF1. This activating electrogenic e vent in response to the rapid onset of the electric potential is an in tegral portion of the reaction sequence producing ATP.