Lithium ion-sugar cotransport via the melibiose transport system in Escherichia coli. Measurement of Li+ transport and specificity.
A lithium ion-selective electrode was constructed using N,N'-diheptyl-N,N'-5,5-tetramethyl-3,7-dioxanonandiamid as a Li+ ionophore. Lithium ion-sugar cotransport via the melibiose transport system was measured with this electrode. Influx of methyl-beta-D-thiogalactoside, methyl-alpha-D-galactoside, methyl-beta-D-galactoside, and D-galactose elicited uptake of Li+. This Li+ uptake was not observed when the melibiose carrier was not present in the cells or the carrier was inactivated. Melibiose caused a small amount of Li+ uptake, indicating that Li+-melibiose cotransport proceeds inefficiently. Raffinose, another substrate, did not cause detectable Li+ transport. In mutant cells which showed altered cation coupling (Niiya, S., Yamasaki, K., Wilson, T. H., and Tsuchiya, T. (1982) J. Biol. Chem. 257, 8902-8906), Li+-melibiose cotransport was clearly demonstrated. Alteration in substrate specificity was also shown in the mutants.
D001693:Biological Transport, Active; D050260:Carbohydrate Metabolism; D004566:Electrodes; D004926:Escherichia coli / Q000378:metabolism*; D007700:Kinetics; D008094:Lithium / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D013329:Structure-Activity Relationship; D027981:Symporters
D026901:Membrane Transport Proteins; D027981:Symporters; C021548:melibiose permease; D008094:Lithium