title: Sites of deamidation and methylation in Tsr, a bacterial chemotaxis sensory transducer.
abstract: The sensory transducer proteins in bacterial chemotaxis undergo two covalent modifications, deamidation and reversible methylation, in response to attractants and repellents. Oligonucleotide-directed mutagenesis was used to alter putative methylation and deamidation sites in one of the transducers to further define these sites and their role in chemotaxis. The mutations, in combination with peptide maps and Edman analysis, have clarified the sites of covalent modification in Tsr. Tsr contains six specific glutamates and glutamines that serve as methyl-accepting sites. An arginine-containing tryptic peptide (R1) has two sites, one at glutamate 493 and a newly located site at glutamate 502. A lysine-containing peptide (K1) has four methyl-accepting sites. Two of the lysine peptide sites are glutamates and can accept methyl groups without deamidation. The other two sites are glutamines and two methyl-accepting sites are created by two distinct deamidations. Both deamidations can occur on the same polypeptide chain. Single glutamate mutants have shown that one deamidation (at glutamine 311) proceeds rapidly, while the other deamidation (at glutamine 297) has a half-life of approximately 60 min under our experimental conditions.
authors.affiliation: Institute of Molecular Biology, University of Oregon, Eugene 97403.
authors.forename: M S
authors.initials: MS
authors.lastname: Rice
authors.forename: F W
authors.initials: FW
authors.lastname: Dahlquist
mesh_terms: D000577:Amides / Q000737:chemistry; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D015153:Blotting, Western; D002633:Chemotaxis; D002851:Chromatography, High Pressure Liquid; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D008745:Methylation; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010449:Peptide Mapping; D014357:Trypsin
chemical_list: D000577:Amides; D001426:Bacterial Proteins; D008565:Membrane Proteins; C057635:Tsr protein, Bacteria; D014357:Trypsin