The Escherichia coli glucose transporter enzyme IICBGlc recruits the global repressor Mlc

In addition to effecting the catalysis of sugar uptake, the bacterial phosp hoenolpyruvate :sugar phosphotransferase system regulates a variety of phys iological processes. Exposure of cells to glucose can result in repression or induction of gene expression, While the mechanism for carbon catabolite repression by glucose was well documented, that for glucose induction was n ot clearly understood in Escherichia coli, Recently, glucose induction of s everal E.coli genes has been shown to be mediated by the global repressor M lc, Here, we elucidate a general mechanism for glucose induction of gene ex pression in E.coli, revealing a novel type of regulatory circuit for gene e xpression mediated by the phosphorylation state-dependent interaction of a membrane-bound protein with a repressor. The dephospho-form of enzyme IICBG lc, but not its phospho-form, interacts directly with Mlc and induces trans cription of Mlc-regulated genes by displacing Mlc from its target sequences . Therefore, the glucose induction of Mlc-regulated genes is caused by deph osphorylation of the membrane-bound transporter enzyme IICBGlc, which direc tly recruits Mlc to derepress its regulon.