title: Dependence on pH of substrate binding to lactose carrier in Escherichia coli cytoplasmic membranes.
abstract: Lactose permease in Escherichia mediates proton-substrate cotransport. The molecular mechanism of this process is not understood. We examined the effect of proton concentration on the binding of a substance analogue to the carrier. The dissociation constant of p-nitrophenyl-alpha-galactoside from the carrier was dependent on pH, with an apparent pKa of 9.7.
mesh_terms: D001692:Biological Transport; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D006863:Hydrogen-Ion Concentration; D026901:Membrane Transport Proteins / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins; D009598:Nitrophenylgalactosides / Q000378:metabolism; D011522:Protons; D027981:Symporters; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D029968:Escherichia coli Proteins; C050221:LacY protein, E coli; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D011522:Protons; D027981:Symporters; D014475:Uncoupling Agents; D009598:Nitrophenylgalactosides; C021499:lactose permease