Chemiosmotic coupling in Methanobacterium thermoautotrophicum: hydrogen-dependent adenosine 5'-triphosphate synthesis by subcellular particles

Abstract

Hydrogenase and the ATP synthetase complex, 2 enzymes essential in ATP generation in M. thermoautotrophicum, were localized in internal membrane systems as shown by cytochemical techniques. Membrane vesicles from this organism possessed hydrogenase and ATPase activity and synthesized ATP driven by H2 oxidation or a K gradient. ATP synthesis depended on anaerobic conditions and could be inhibited in membrane vesicles by uncouplers, nigericin, or the ATPase inhibitor N,N''-dicyclohexylcarbodiimide. The presence of an ADP-ATP translocase was postulated. With fluorescent dyes, a membrane potential and pH gradient were demonstrated.