title: Effect of substitution of Asn for Arg-276 in the cefotaxime-hydrolyzing class A beta-lactamase CTX-M-4.
abstract: The effect of substitution of asparagine for arginine at position 276 (Ambler's numbering) on the properties of the extended-spectrum beta-lactamase CTX-M-4 was studied. Compared with CTX-M-4, the mutant beta-lactamase CTX-M-4(R276N) conferred lower levels of resistance to cefotaxime, ceftriaxone and aztreonam while the levels of resistance to penicillins and penicillin-inhibitor combinations were similar. Arg-276-->Asn substitution rendered CTX-M-4 slightly less susceptible to inhibition by clavulanate and tazobactam. It also caused a three-fold reduction in the relative rate of hydrolysis of cefotaxime. These results indicate that Arg-276 in CTX-M-type beta-lactamases may be implicated in hydrolysis of oxyimino-beta-lactams; they do not, however, support the hypothesis that Arg-276 is the functional equivalent of Arg-244 found in other class A beta-lactamases.
authors.affiliation: Department of Microbiology, Medical School, University of Athens, Greece.
authors.forename: M
authors.initials: M
authors.lastname: Gazouli
authors.forename: N J
authors.initials: NJ
authors.lastname: Legakis
authors.forename: L S
authors.initials: LS
authors.lastname: Tzouvelekis
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics*; D001120:Arginine / Q000737:chemistry*; D001216:Asparagine / Q000737:chemistry*; D001426:Bacterial Proteins; D002439:Cefotaxime / Q000378:metabolism* / Q000494:pharmacology; D002511:Cephalosporins / Q000378:metabolism* / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology; D016296:Mutagenesis; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D002511:Cephalosporins; D065093:beta-Lactamase Inhibitors; D001216:Asparagine; D001120:Arginine; C112790:CTX-M-4 protein, Salmonella typhimurium; D001618:beta-Lactamases; D002439:Cefotaxime