title: The role of the membrane-bound hydrogenase in the energy-conserving oxidation of molecular hydrogen by Escherichia coli.
abstract: H2-dependent reduction of fumarate and nitrate by spheroplasts from Escherichia coli is coupled to the translocation of protons across the cytoplasmic membrane. The leads to H+/2e- stoicheiometry (g-ions of H+ translocated divided by mol of H2 added) is approx. 2 with fumarate and approx. 4 with nitrate as electron acceptor. This proton translocation is dependent on H2 and a terminal electron acceptor and is not observed in the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone and the respiratory inhibitor 2-n-heptyl-4-hydroxyquinoline N-oxide. H2-dependent reduction of menadione and ubiquinone-1 is coupled to a protonophore-sensitive, but 2-n-heptyl-4-hydroxy-quinoline N-oxide-insensitive, proton translocation with leads to H+/2e- stoicheiometry of approx. 2. H2-dependent reduction of Benzyl Viologen (BV++) to its radical (BV+) liberates protons at the periplasmic aspect of the cytoplasmic membrane according to the reaction: H2 + 2BV++ leads to 2H+ + 2BV+. It is concluded that the effective proton translocation observed in the H2-oxidizing segment of the anaerobic respiratory chain of Escherichia coli arises as a direct and inevitable consequence of transmembranous electron transfer between protolytic reactions that are spatially separated by a membrane of low proton-permeability.
mesh_terms: D004926:Escherichia coli / Q000201:enzymology*; D005650:Fumarates / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism*; D007425:Intracellular Membranes / Q000201:enzymology; D008954:Models, Biological; D009566:Nitrates / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D011522:Protons; D013104:Spheroplasts / Q000201:enzymology; D014812:Vitamin K / Q000378:metabolism
chemical_list: D005650:Fumarates; D009566:Nitrates; D011522:Protons; D014812:Vitamin K; D006859:Hydrogen; D010088:Oxidoreductases