title: Oxidative phosphorylation by membrane vesicles from Bacillus alcalophilus.
abstract: ADP and Pi-loaded membrane vesicles from t-malate-grown Bacillus alcalophilus synthesized ATP upon energization with ascorbate/N,N,N',N'-tetra-methyl-P-phenylenediamine. ATP synthesis occurred over a range of external pH from 6.0 to 11.0, under conditions in which the total protonmotive force delta-mu-H+ was as low as -30 mV. The phosphate potentials (delta Gp) were calculated to be 11 and 12 kcal/mol at pH 10.5 and 9.0, respectively, whereas the delta-mu-H+ values in vesicles at these two pH values were quite different (-40 +/- 20 mV at pH 10.5 and -125 +/- 20 mV at pH 9.0). ATP synthesis was inhibited by KCN, gramicidin, and by N,N1-dicyclohexylcarbodiimide. Inward translocation of protons, concomitant with ATP synthesis, was demonstrated using direct pH monitoring and fluorescence methods. No dependence upon the presence of Na+ or K+ was found. Thus, ATP synthesis in B. alcalophilus appears to involve a proton-translocating ATPase which functions at low delta-mu-H+.
mesh_terms: D001407:Bacillus / Q000378:metabolism*; D002151:Calorimetry; D002462:Cell Membrane / Q000378:metabolism; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004579:Electron Transport; D006096:Gramicidin / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials / Q000187:drug effects; D010085:Oxidative Phosphorylation / Q000187:drug effects; D011190:Potassium Cyanide / Q000494:pharmacology; D013816:Thermodynamics
chemical_list: D006096:Gramicidin; D004024:Dicyclohexylcarbodiimide; D011190:Potassium Cyanide