Membrane transport of p-nitrophenyl-alpha-galactoside by the melibiose carrier of Escherichia coli.
p-Nitrophenyl-alpha-galactoside (alpha-pNPG) was found to be a substrate for the melibiose transport system of Escherichia coli. This sugar enters induced cells via the carrier and is split by alpha-galactosidase to galactose and p-nitrophenol. In mutant cells lacking the alpha-galactosidase [3H]-alpha-pNPG accumulated to concentrations 15 times higher than the external medium. The transport of alpha-pNPG is inhibited by both Na+ and Li+. Na+ (10 mM) reduced the Km for alpha-pNPG from 0.45 to 0.18 mM and reduced the Vmax from 6.7 nmoles/min/mg dry wt to a value of 3.0.
D001693:Biological Transport, Active / Q000187:drug effects; D004187:Disaccharides / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D006027:Glycosides / Q000378:metabolism*; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology; D008553:Melibiose / Q000378:metabolism*; D009154:Mutation; D009598:Nitrophenylgalactosides / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology
D004187:Disaccharides; D006027:Glycosides; D009598:Nitrophenylgalactosides; D008553:Melibiose; D008094:Lithium; D012964:Sodium