title: The electrochemical proton gradient generated by the fumarate-reductase system in Escherichia coli and its bioenergetic implications.
abstract: Proton translocation, coupled to electron transfer in the fumarate reductase system, generates and electrochemical potential gradient for protons (delta approximately mu H+). The magnitude of this free energy gradient has been determined in the Escherichia coli strains ML 208-225 and AN 283. The measurements were performed in (inverted) membrane particles, right-side out membrane vesicles and EDTA-treated intact cells in external media of various ionic compositions and pH. The maximal values of delta approximately mu H+ in these three systems were +103, -101 and -105 mV, respectively. This implicates that in E. coli, upon transition from oxygen to fumarate as electron acceptor, the magnitude of the delta approximately mu H+ decreases considerably. This change of delta approximately mu H+ has substantial consequences for the cellular metabolism.
mesh_terms: D002462:Cell Membrane / Q000201:enzymology; D004492:Edetic Acid / Q000494:pharmacology; D004734:Energy Metabolism; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D011522:Protons; D013385:Succinate Dehydrogenase / Q000378:metabolism*
chemical_list: D011522:Protons; D004492:Edetic Acid; D013385:Succinate Dehydrogenase