title: Maltose chemotaxis involves residues in the N-terminal and C-terminal domains on the same face of maltose-binding protein.
abstract: The periplasmic maltose-binding protein (MBP) of Escherichia coli is the recognition component of the maltose chemoreceptor and of the active transport system for maltose. It interacts with the Tar chemotactic signal transducer and the integral cytoplasmic-membrane components (the MalF and MalG proteins) of the maltose transport system. Maltose binds in a cleft between the globular N-terminal and C-terminal domains of MBP, which are connected by a moveable hinge. The two domains undergo a large motion relative to one another as the protein moves from the open, unbound state to the closed, ligand-bound state. We generated, by doped-primer mutagenesis, amino acid substitutions that specifically disrupt the chemotactic function of MBP. These substitutions cluster in two well-defined regions that are nearly contiguous on the surface of MBP in its closed conformation. One region is in the N-terminal domain and one is in the C-terminal domain. The distance between the two regions is expected to change substantially as the protein goes from the open to the closed form. These results support a model in which ligand binding brings two recognition sites on MBP into the proper spatial relationship to interact with complementary sites on Tar. Mutations in MBP that appear to cause defects in interaction with MalF and MalG are distributed differently from mutations that primarily affect maltose taxis. We conclude that the regions of MBP that contact Tar and those that contact MalF and MalG are adjacent on the face of the protein opposite the hinge connecting the two domains and that those regions are largely, although perhaps not entirely, distinct.
authors.affiliation: Department of Biology, Texas A & M University, College Station 77843-3258.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: C
authors.initials: C
authors.lastname: Conway
authors.forename: M
authors.initials: M
authors.lastname: Rosato
authors.forename: Y
authors.initials: Y
authors.lastname: Suh
authors.forename: M D
authors.initials: MD
authors.lastname: Manson
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism*; D002633:Chemotaxis / Q000235:genetics; D003062:Codon / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D007700:Kinetics; D008320:Maltose / Q000378:metabolism* / Q000494:pharmacology; D058619:Maltose-Binding Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D016297:Mutagenesis, Site-Directed; D033902:Periplasmic Binding Proteins; D011487:Protein Conformation; D017433:Protein Structure, Secondary
chemical_list: D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D003062:Codon; D029968:Escherichia coli Proteins; C461619:MalE protein, E coli; C079123:MalG protein, E coli; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; C461599:maltose transport system, E coli; D008320:Maltose