Deduction of consensus binding sequences on proteins that bind IIA Glc of the phospho enol pyruvate:sugar phosphotransferase system by cysteine scanning mutagenesis of Escherichia coli lactose permease

Mediated by the protein IIA Glc , the phospho enol pyruvate:sugar phosphotransferase system plays a role in the regulation of activity of other sugar transport systems in Escherichia coli . By using a direct binding assay, a collection of single-Cys replacement mutants in cytoplasmic loops of lactose permease were evaluated for their capacity to bind IIA Glc . Selected Cys replacements in loops IV/V or VI/VII result in loss of binding activity. Analysis of the mutagenesis results together with multiple sequence alignments of a family of proteins that interacts with IIA Glc provides the basis for developing two regions of consensus sequence in those partner proteins necessary for binding to IIA Glc . The requirement for two interaction regions is interpreted in the regulatory framework of a substrate-dependent conformational change that brings those two regions into an orientation optimal for binding IIA Glc .