PDBsum entry 1ghm

Hydrolase

PDB id: 1ghm

Contents

Protein chain

257 a.a. *

Ligands

SO4 ×5

CO3

CED

Waters ×326

* Residue conservation analysis

PDB id:

1ghm

Name:

Hydrolase

Title:

Structures of the acyl-enzyme complex of the staphylococcus aureus beta-lactamase mutant glu166asp:asn170gln with degraded cephaloridine

Structure:

Beta-lactamase. Chain: a. Synonym: penicillinase. Engineered: yes. Mutation: yes

Source:

Staphylococcus aureus. Organism_taxid: 1280. Strain: pc1. Gene: blaz. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.86Å R-factor: 0.188 R-free: 0.241

Authors:

C.C.H.Chen,O.Herzberg

Key ref:

C.C.Chen and O.Herzberg (2001). Structures of the acyl-enzyme complexes of the Staphylococcus aureus beta-lactamase mutant Glu166Asp:Asn170Gln with benzylpenicillin and cephaloridine. Biochemistry, 40, 2351-2358. PubMed id: 11327855 DOI: 10.1021/bi002277h

Date:

19-Dec-00 Release date: 04-Apr-01

Protein chain

P00807  (BLAC_STAAU) -  Beta-lactamase from Staphylococcus aureus

Seq: 281 a.a.

Struc: 257 a.a.*

* PDB and UniProt seqs differ at 2 residue positions (black crosses)

Enzyme reactions

• Enzyme class: E.C.3.5.2.6 - beta-lactamase.
• Pathway: Penicillin Biosynthesis and Metabolism
• Reaction: a beta-lactam + H2O = a substituted beta-amino acid
• Cofactor: Zn(2+)

DOI no: 10.1021/bi002277h

Biochemistry 40:2351-2358 (2001)

PubMed id: 11327855

Structures of the acyl-enzyme complexes of the Staphylococcus aureus beta-lactamase mutant Glu166Asp:Asn170Gln with benzylpenicillin and cephaloridine.

C.C.Chen, O.Herzberg.

ABSTRACT

The serine-beta-lactamases hydrolyze beta-lactam antibiotics in a reaction that proceeds via an acyl-enzyme intermediate. The double mutation, E166D:N170Q, of the class A enzyme from Staphylococcus aureus results in a protein incapable of deacylation. The crystal structure of this beta-lactamase, determined at 2.3 A resolution, shows that except for the mutation sites, the structure is very similar to that of the native protein. The crystal structures of two acyl-enzyme adducts, one with benzylpenicillin and the other with cephaloridine, have been determined at 1.76 and 1.86 A resolution, respectively. Both acyl-enzymes show similar key features, with the carbonyl carbon atom of the cleaved beta-lactam bond covalently bound to the side chain of the active site Ser70, and the carbonyl oxygen atom in an oxyanion hole. The thiadolizine ring of the cleaved penicillin is located in a slightly different position than the dihydrothiazine ring of cephaloridine. Consequently, the carboxylate moieties attached to the rings form different sets of interactions. The carboxylate group of benzylpenicillin interacts with the side chain of Gln237. The carboxylate group of cephaloridine is located between Arg244 and Lys234 side chains and also interacts with Ser235 hydroxyl group. The interactions of the cephaloridine resemble those seen in the structure of the acyl-enzyme of beta-lactamase from Escherichia coli with benzylpenicillin. The side chains attached to the cleaved beta-lactam rings of benzylpenicillin and cephaloridine are located in a similar position, which is different than the position observed in the E. coli benzylpenicillin acyl-enzyme complex. The three modes of binding do not show a trend that explains the preference for benzylpenicillin over cephaloridine in the class A beta-lactamases. Rather, the conformational variation arises because cleavage of the beta-lactam bond provides additional flexibility not available when the fused rings are intact. The structural information suggests that specificity is determined prior to the cleavage of the beta-lactam ring, when the rigid fused rings of benzylpenicillin and cephaloridine each form different interactions with the active site.