title: Crystal structure of the catalytic domain of the chemotaxis receptor methylesterase, CheB.
abstract: Signaling activity of bacterial chemotaxis transmembrane receptors is modulated by reversible covalent modification of specific receptor glutamate residues. The level of receptor methylation results from the activities of a specific S-adenosylmethionine-dependent methyltransferase, CheR, and the CheB methylesterase, which catalyzes hydrolysis of receptor glutamine or methylglutamate side-chains to glutamic acid. The CheB methylesterase belongs to a large family of response regulator proteins in which N-terminal regulatory domains control the activities of C-terminal effector domains. The crystal structure of the catalytic domain of the Salmonella typhimurium CheB methylesterase has been determined at 1.75 A resolution. The domain has a modified, doubly wound alpha/beta fold in which one of the helices is replaced by an anti-parallel beta-hairpin. Previous biochemical and mutagenesis data, suggest that the methylester hydrolysis catalyzed by CheB proceeds through a mechanism involving a serine nucleophile. The methylesterase active site is tentatively identified as a cleft at the C-terminal edge of the beta-sheet containing residues Ser164, His190 and Asp286. The three-dimensional fold, and the arrangement of residues within the catalytic triad distinguishes the CheB methylesterase from any previously described serine protease or serine hydrolase.
authors.affiliation: Department of Biochemistry, University of Medicine and Dentistry, New Jersey-Robert Wood Johnson Medical School,Piscataway USA.
authors.forename: A H
authors.initials: AH
authors.lastname: West
authors.forename: E
authors.initials: E
authors.lastname: Martinez-Hackert
authors.forename: A M
authors.initials: AM
authors.lastname: Stock
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D012486:Salmonella typhimurium / Q000201:enzymology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D002265:Carboxylic Ester Hydrolases; C041144:chemotactic protein methylesterase