title: Effect of uncoupler on "downhill" substrate efflux of Escherichia coli is dependent on (Mg2+, Ca2+). Adenosine triphosphatase.
abstract: Previous studies have shown that mutations in the unc gene of Escherichia coli K12 cause defects in energy transduction as well as a membrane-bound (Mg2+, Ca2+)-adenosine triphosphatase. We studied the effect of this mutation on the "downhill" efflux of methyl-beta-D-galactopyranoside, a suboli K12 did not show significant differences in substrate influx of efflux, a differential effect of an uncoupler, 2,4-dinitrophenol was demonstrated. In contrast to the unc+, dinitrophenol failed to inhibit significantly the rate coefficient of efflux in the unc- strain. Analysis of spontaneous unc+ revertants of the unc- mutant provided additional evidence that a functional unc gene is necessary for dinitrophenol inhibition of efflux. Other uncouplers tested in the unc+ strain showed different effects on efflux. While arsenate, azide and carbonyl cyanide p-trifluoromethoxyphenulhydrazone caused little or no effect, 2,4-dibromophenol and pentachlorophenol increased efflux by a considerable factor.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001149:Arsenates / Q000494:pharmacology; D001386:Azides / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D004140:Dinitrophenols / Q000494:pharmacology*; D004926:Escherichia coli; D006842:Hydrocarbons, Brominated / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008756:Methylgalactosides / Q000378:metabolism*; D008759:Methylglycosides / Q000378:metabolism*; D009154:Mutation; D010416:Pentachlorophenol / Q000494:pharmacology; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D001149:Arsenates; D001386:Azides; D004140:Dinitrophenols; D006842:Hydrocarbons, Brominated; D008756:Methylgalactosides; D008759:Methylglycosides; D014475:Uncoupling Agents; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D010416:Pentachlorophenol; D000251:Adenosine Triphosphatases; D008274:Magnesium; D002118:Calcium