1rcj

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spinqualitylabelsall models 1rcj, resolution 1.63Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal structure of E166A mutant of SHV-1 beta-lactamase with the trans-enamine intermediate of tazobactam

Overview

Many pathogenic bacteria develop antibiotic resistance by utilizing, beta-lactamases to degrade penicillin-like antibiotics. A commonly, prescribed mechanism-based inhibitor of beta-lactamases is tazobactam, which can function either irreversibly or in a transient manner. We have, demonstrated previously that the reaction between tazobactam and a, deacylation deficient variant of SHV-1 beta-lactamase, E166A, could be, followed in single crystals using Raman microscopy [Helfand, M. S., et al., (2003) Biochemistry 42, 13386-13392]. The Raman data show that maximal, populations of an enamine-like intermediate occur 20-30 min after "soaking, in" has commenced. By flash-freezing crystals in this time frame, we were, able to trap the enamine species. The resulting 1.63 A resolution crystal, structure revealed tazobactam covalently bound in the trans-enamine, intermediate state with close to 100% occupancy in the active site. The, Raman data also indicated that tazobactam forms a larger population of, enamine than sulbactam or clavulanic acid does and that tazobactam's, intermediate is also the most long-lived. The crystal structure provides a, rationale for this finding since only tazobactam is able to form favorable, intra- and intermolecular interactions in the active site that stabilize, this trans-enamine intermediate. These interactions involve both the, sulfone and triazolyl groups that distinguish tazobactam from clavulanic, acid and sulbactam, respectively. The observed stabilization of the, transient intermediate of tazobactam is thought to contribute to, tazobactam's superior in vitro and in vivo clinical efficacy., Understanding the structural details of differing inhibitor effectiveness, can aid the design of improved mechanism-based beta-lactamase inhibitors.

About this Structure

1RCJ is a Single protein structure of sequence from Klebsiella pneumoniae with MA4 and TBI as ligands. Active as Beta-lactamase, with EC number 3.5.2.6 Full crystallographic information is available from OCA.

Reference

Tazobactam forms a stoichiometric trans-enamine intermediate in the E166A variant of SHV-1 beta-lactamase: 1.63 A crystal structure., Padayatti PS, Helfand MS, Totir MA, Carey MP, Hujer AM, Carey PR, Bonomo RA, van den Akker F, Biochemistry. 2004 Feb 3;43(4):843-8. PMID:14744126

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