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Publication Abstract from PubMed

The beta-lactamase of Mycobacterium tuberculosis, BlaC, is susceptible to inhibition by clavulanic acid. The ability of this enzyme to escape inhibition through mutation was probed using error-prone PCR combined with functional screening in Escherichia coli The variant that was found to confer most inhibitor resistance, K234R, as well as variant G132N that was found previously, were characterized using X-ray crystallography and NMR relaxation experiments to probe structural and dynamic properties. The G132N mutant exists in solution in two, almost equally populated conformations that exchange with a rate of ca 88 s(-1) The conformational change affects a broad region of the enzyme. The crystal structure reveals that the Asn132 side chain forces the peptide bond between Ser104 and Ile105 in a cis-conformation. The crystal structure suggests multiple conformations for several side chains (e.g. Ser104, Ser130) and a short loop (214-216). In the K234R mutant, the active site dynamics are significantly diminished with respect to the wild type enzyme. These results show that multiple evolutionary routes are available to increase inhibitor resistance in BlaC and that active site dynamics on the millisecond time scale are not required for catalytic function.

Two beta-lactamase variants with reduced clavulanic acid inhibition display different millisecond dynamics.,Elings W, Chikunova A, van Zanten DB, Drenth R, Ahmad MUD, Blok AJ, Timmer M, Perrakis A, Ubbink M Antimicrob Agents Chemother. 2021 May 24. pii: AAC.02628-20. doi:, 10.1128/AAC.02628-20. PMID:34031049^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.