title: Molecular structure of the acyl-enzyme intermediate in beta-lactam hydrolysis at 1.7 A resolution.
abstract: The X-ray crystal structure of the molecular complex of penicillin G with a deacylation-defective mutant of the RTEM-1 beta-lactamase from Escherichia coli shows how these antibiotics are recognized and destroyed. Penicillin G is covalently bound to Ser 70 0 gamma as an acyl-enzyme intermediate. The deduced catalytic mechanism uses Ser 70 0 gamma as the attacking nucleophile during acylation. Lys 73 N zeta acts as a general base in abstracting a proton from Ser 70 and transferring it to the thiazolidine ring nitrogen atom via Ser 130 0 gamma. Deacylation is accomplished by nucleophilic attack on the penicilloyl carbonyl carbon by a water molecule assisted by the general base, Glu 166.
authors.affiliation: Department of Biochemistry, University of Alberta, Edmonton, Canada.
authors.forename: N C
authors.initials: NC
authors.lastname: Strynadka
authors.forename: H
authors.initials: H
authors.lastname: Adachi
authors.forename: S E
authors.initials: SE
authors.lastname: Jensen
authors.forename: K
authors.initials: K
authors.lastname: Johns
authors.forename: A
authors.initials: A
authors.lastname: Sielecki
authors.forename: C
authors.initials: C
authors.lastname: Betzel
authors.forename: K
authors.initials: K
authors.lastname: Sutoh
authors.forename: M N
authors.initials: MN
authors.lastname: James
mesh_terms: D000215:Acylation; D000595:Amino Acid Sequence; D001665:Binding Sites; D002384:Catalysis; D003461:Crystallography; D004926:Escherichia coli / Q000201:enzymology; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010400:Penicillin G / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012694:Serine / Q000737:chemistry; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction; D001618:beta-Lactamases / Q000737:chemistry / Q000648:ultrastructure*
chemical_list: D012694:Serine; D001618:beta-Lactamases; D010400:Penicillin G