Regulation of galactoside transport by the PTS.

Inducer exclusion, regulation of activity of transporter, is mediated by phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS). To elucidate the molecular mechanism of the inducer exclusion, numerous biochemical and genetic studies have been performed. It is now well known that non-phosphorylated IIA(Glc) inhibits the transport via direct binding to the transporter. Analysis of inducer exclusion resistant mutants of lactose transporter and melibiose transporter in Escherichia coli and Salmonella typhimurium revealed amino acid residues that are involved in the interaction with IIA(Glc). It is concluded that there are multiple interaction sites for IIA(Glc) in these transporters.