title: Hydrolysis and synthesis of ATP by membrane-bound ATPase from a motile Streptococcus.
abstract: ATPase was detected in the membranes of a motile Streptococcus. Maximal enzymic activity was observed at pH 8 and ATP/Mg2+ ratio of 2. Mn2+ and Ca2+ could replace Mg2+ to some extent. Besides ATP, GTP and ITP were substrates. The enzyme was inhibited by N,N'-dicyclohexylcarbodiimide but not by sodium azide, uncouplers or bathophenanthroline. An electrochemical gradient of protons, which was artificially imposed across the membranes of Streptococcus cells by manipulation of either the K+ diffusion potential or the transmembrane pH gradient, led to ATP synthesis. ATP synthesis was abolished by proton  conductors, an inhibitor of the ATPase or an increase in the extracellular K+ concentration. A comparison between the phosphate potential and the electrochemical proton gradient showed that the data found are in agreement with a stoichiometry of 2 protons translocated per molecule ATP synthesized.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000096:biosynthesis / Q000378:metabolism*; D002462:Cell Membrane / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008564:Membrane Potentials; D009068:Movement; D013291:Streptococcus / Q000378:metabolism* / Q000502:physiology; D014475:Uncoupling Agents / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D014475:Uncoupling Agents; D014634:Valinomycin; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases