The CF0 Energy-Transfer Inhibitors DCCD and Venturicidin Greatly Vary in their Effect on Proton Flux Across the Thylakoid Membrane

Illuminated thylakoids, like other energy transducing membranes, couple electron transport to ATP synthesis via the formation of an electrochemical proton gradient that is utilized to make ATP. Electron transport is coupled to proton translocation into the thylakoid lumen (proton electrochemical gradient formation), and proton flux down the electrochemical gradient is coupled to ATP synthesis. When the gradient is not utilized, ΔpH increases and electron transport slows down. Previously It was shown that. at a high external pH and a large proton gradient, when no ATP is synthesized, electron transport proceeds at high rates, a phenomenon termed ‘slip (1–3). Nevertheless, when proton flow through the ATP synthase is blocked with compounds known as energy transfer inhibitors, ΔpH will increase further and electron transport will slow down.