Energy Transduction in Chlorobium limicola: Role of Membrane-bound Adenosine Triphosphatase and the Proton Electrochemical Gradient

Department of Biochemistry, University of Hull, Hull HU6 7RX ABSTRACT Photophosphorylation in vivo by Chlorobium limicola was inhibited by lipophilic cations and the energy-transfer inhibitors diphenylphosphorylazide, Dio-9, 4-chloro-7-nitrobenzofurazan and chlorhexidene. Membrane-bound ATPase activity was also inhibited by these energy-transfer inhibitors. The formation of a membrane potential was stimulated approximately 1.7-fold on illumination, rising to a value between –110 and –150 mV. The sensitivity of the processes producing this membrane potential to uncouplers, energy-transfer inhibitors and 2-heptyl-4-hydroxyquinoline- N -oxide was measured in the light and the dark.