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1i2w
From Proteopedia
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| , resolution 1.70Å | |||||||
|---|---|---|---|---|---|---|---|
| Ligands: | and | ||||||
| Activity: | Beta-lactamase, with EC number 3.5.2.6 | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
BETA-LACTAMASE FROM BACILLUS LICHENIFORMIS BS3 COMPLEXED WITH CEFOXITIN
Overview
The 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.
About this Structure
1I2W is a Single protein structure of sequence from Bacillus licheniformis. Full crystallographic information is available from OCA.
Reference
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
Page seeded by OCA on Thu Mar 20 11:44:51 2008
