title: Aspartate and maltose-binding protein interact with adjacent sites in the Tar chemotactic signal transducer of Escherichia coli.
abstract: The Tar protein of Escherichia coli is a chemotactic signal transducer that spans the cytoplasmic membrane and mediates responses to the attractants aspartate and maltose. Aspartate binds directly to Tar, whereas maltose binds to the periplasmic maltose-binding protein, which then interacts with Tar. The Arg-64, Arg-69, and Arg-73 residues of Tar have previously been shown to be involved in aspartate sensing. When lysine residues are introduced at these positions by site-directed mutagenesis, aspartate taxis is disrupted most by substitution at position 64, and maltose taxis is disrupted most by substitution at position 73. To explore the spatial distribution of ligand recognition sites on Tar further, we performed doped-primer mutagenesis in selected regions of the tar gene. A number of mutations that interfere specifically with aspartate taxis (Asp-), maltose taxis (Mal-), or both were identified. Mutations affecting residues 64 to 73 or 149 to 154 in the periplasmic domain of Tar are associated with an Asp- phenotype, whereas mutations affecting residues 73 to 83 or 141 to 150 are associated with a Mal- phenotype. We conclude that aspartate and maltose-binding protein interact with adjacent and partially overlapping regions in the periplasmic domain of Tar to initiate attractant signalling.
authors.affiliation: Department of Biology, Texas A&M University, College Station 77843-3258.
authors.forename: P
authors.initials: P
authors.lastname: Gardina
authors.forename: C
authors.initials: C
authors.lastname: Conway
authors.forename: M
authors.initials: M
authors.lastname: Kossman
authors.forename: M
authors.initials: M
authors.lastname: Manson
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000595:Amino Acid Sequence; D001224:Aspartic Acid / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics*; D002628:Chemoreceptor Cells; D002633:Chemotaxis / Q000187:drug effects / Q000235:genetics*; D004252:DNA Mutational Analysis; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D029968:Escherichia coli Proteins; D008320:Maltose / Q000494:pharmacology; D058619:Maltose-Binding Proteins; D008565:Membrane Proteins / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D016297:Mutagenesis, Site-Directed; D033902:Periplasmic Binding Proteins; D011956:Receptors, Cell Surface; D015398:Signal Transduction
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C461619:MalE protein, E coli; D058619:Maltose-Binding Proteins; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; D011956:Receptors, Cell Surface; C057331:Tar protein, E coli; C461599:maltose transport system, E coli; D001224:Aspartic Acid; D008320:Maltose