Role of Na+ and Li+ in thiomethylgalactoside transport by the melibiose transport system of Escherichia coli.
Thiomethyl-beta-galactoside (TMG) accumulation via the melibiose transport system was studied in lactose transport-negative strains of Escherichia coli. TMG uptake by either intact cells or membrane vesicles was markedly stimulated by Na+ or Li+ between pH 5.5 and 8. The Km for uptake of TMG was approximately 0.2 mM at an external Na+ concentration of 5 mM (pH 7). The alpha-galactosides, melibiose, methyl-alpha-galactoside, and o-nitrophenyl-alpha-galactoside had a high affinity for this system whereas lactose, maltose and glucose had none. Evidence is presented for Li+-TMG or Na+-TMG cotransport.
D001693:Biological Transport, Active / Q000187:drug effects; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D004187:Disaccharides / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D005697:Galactosides / Q000378:metabolism*; D006027:Glycosides / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008094:Lithium / Q000378:metabolism* / Q000494:pharmacology; D008564:Membrane Potentials; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology; D013439:Sulfhydryl Reagents / Q000494:pharmacology
D004187:Disaccharides; D005697:Galactosides; D006027:Glycosides; D013439:Sulfhydryl Reagents; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D008094:Lithium; D012964:Sodium