Conformational change of the chloroplast ATP synthase on the enzyme activation process detected by the trypsin sensitivity of the γ subunit

Abstract

ΔμH + is known to stimulate the enzyme activity of chloroplast ATP synthase in addition to its important role as energy supply for ATP synthesis. In the present study, we focused on the relationship between the proton translocation via the membrane sector of ATP synthase, F o, and the conformational change of the central stalk subunit γ. The conformational change of CF 1 mainly at the γ subunit was induced by the proton flow via F o in the absence of substrates. The effects of inhibitors on CF o or CF 1 for this conformational change were also examined. The observed conformational change was partially suppressed by ADP binding. From these results, we propose the ΔμH +-dependent conformational change of CF 1 on the enzyme activation process, which is affected by both ADP binding to the catalytic sites and proton flow via F o portion.