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BETA-LACTAMASE FROM BACILLUS LICHENIFORMIS BS3 COMPLEXED WITH CEFOXITIN
Structural highlights
Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe Bacillus licheniformis BS3 beta-lactamase catalyzes the hydrolysis of the beta-lactam ring of penicillins, cephalosporins, and related compounds. The production of beta-lactamases is the most common and thoroughly studied cause of antibiotic resistance. Although they escape the hydrolytic activity of the prototypical Staphylococcus aureus beta-lactamase, many cephems are good substrates for a large number of beta-lactamases. However, the introduction of a 7alpha-methoxy substituent, as in cefoxitin, extends their antibacterial spectrum to many cephalosporin-resistant Gram-negative bacteria. The 7alpha-methoxy group selectively reduces the hydrolytic action of many beta-lactamases without having a significant effect on the affinity for the target enzymes, the membrane penicillin-binding proteins. We report here the crystallographic structures of the BS3 enzyme and its acyl-enzyme adduct with cefoxitin at 1.7 A resolution. The comparison of the two structures reveals a covalent acyl-enzyme adduct with perturbed active site geometry, involving a different conformation of the omega-loop that bears the essential catalytic Glu166 residue. This deformation is induced by the cefoxitin side chain whose position is constrained by the presence of the alpha-methoxy group. The hydrolytic water molecule is also removed from the active site by the 7beta-carbonyl of the acyl intermediate. In light of the interactions and steric hindrances in the active site of the structure of the BS3-cefoxitin acyl-enzyme adduct, the crucial role of the conserved Asn132 residue is confirmed and a better understanding of the kinetic results emerges. Crystal structures of the Bacillus licheniformis BS3 class A beta-lactamase and of the acyl-enzyme adduct formed with cefoxitin.,Fonze E, Vanhove M, Dive G, Sauvage E, Frere JM, Charlier P Biochemistry. 2002 Feb 12;41(6):1877-85. PMID:11827533[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences | ||||||||||||||||||||
