Open AccessProton translocation coupled to the oxidation of carbon monoxide to CO 2 and H 2 in Methanosarcina barkeri
Author(s) -
BOTT Michael,
THAUER Rudolf K.
Publication year - 1989
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1989.tb14576.x
Subject(s) - protonophore , methanosarcina barkeri , chemistry , valinomycin , chemiosmosis , carbon monoxide , inorganic chemistry , carbon monoxide dehydrogenase , proton , atp synthase , nuclear chemistry , methanogenesis , biochemistry , catalysis , membrane , methane , organic chemistry , enzyme , physics , quantum mechanics
Cell suspensions of acetate‐grown Methanosarcina barkeri mediate the conversion of CO and H 2 O to CO 2 and H 2 . The reaction is coupled with the phosphorylation of ADP. Evidence is presented that CO oxidation by the cells is associated with the transient acidification of the suspension medium. Up to 2 mol vectorial protons were measured/mol CO oxidized when the transmembrane electrical gradient was kept low by the addition of valinomycin (20 nmol/mg protein) and KCl (200 mM) or of KSCN (50 mM). No transient acidification was observed in the presence of the protonophore tetrachlorosalicylanilide which stimulated rather than inhibited CO oxidation. Proton extrusion remained unaltered when the proton‐translocating ATPase was specifically inhibited by dicyclohexylcarbodiimide. The latter finding indicates that proton translocation is associated with CO conversion to CO 2 and H 2 rather than with ATP hydrolysis in the cells. The data substantiate that the coupling of CO oxidation with ADP phosphorylation in M. barkeri occurs via a chemiosmotic mechanism.