The kinetics of adenine nucleotide binding to chloroplast ATPase, CF 0-CF 1, during the illumination and post illumination periodi in isolated pea thylakoids

Abstract

The steady-state binding of [2- 3H]ADP to thylakoid membrane protonmotive ATPase (CF 0-CF 1) was studied using a quench technique similar to that developed by Strotmann, Bickel-Sandkotter and Shoshan (FEBS Lett. 101 (1979) 316–320). The amount of adenine nucleotide bound in the light and post-illumination dark period is shown to depend on the efficaency of uncoupling when the reaction is quenched. Previous observations that post-illumination binding of [2- 3H]ADP displays a fast and a slow phase of binding were confirmed only when uncoupling efficiency was relatively low during quenching. When uncoupling efficiency is increased, the fast phase of dark [2- 3H]ADP binding is abolished, and correspondingly more nucleotide appears to be bound upon quenching in the light. The previous assignment of the observed kinetic phases to different species of enzyme-nucleotide complex has been reassessed in the light of this new data.