Structural and biochemical characterization of VIM‐26 shows that Leu224 has implications for the substrate specificity of VIM metallo‐β‐lactamases

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Abstract

During the last decades antimicrobial resistance has become a global health problem. Metallo‐β‐lactamases ( MBL s) which are broad‐spectrum β‐lactamases that inactivate virtually all β‐lactams including carbapenems, are contributing to this health problem. In this study a novel MBL variant, termed VIM ‐26, identified in a Klebsiella pneumoniae isolate was studied. VIM ‐26 belongs to the Verona integron‐encoded metallo‐β‐lactamase ( VIM ) family of MBL s and is a His224Leu variant of the well‐characterized VIM ‐1 variant. In this study, we report the kinetic parameters, minimum inhibitory concentrations and crystal structures of a recombinant VIM ‐26 protein, and compare them to previously published data on VIM ‐1, VIM ‐2 and VIM ‐7. The kinetic parameters and minimum inhibitory concentration determinations show that VIM ‐26, like VIM ‐7, has higher penicillinase activity but lower cephalosporinase activity than VIM ‐1 and VIM ‐2. The four determined VIM ‐26 crystal structures revealed mono‐ and di‐zinc forms, where the Zn1 ion has distorted tetrahedral coordination geometry with an additional water molecule (W2) at a distance of 2.6–3.7 Å, which could be important during catalysis. The R2 drug binding site in VIM ‐26 is more open compared to VIM ‐2 and VIM ‐7 and neutrally charged due to Leu224 and Ser228. Thus, the VIM ‐26 drug binding properties are different from the VIM ‐2 (Tyr224/Arg228) and VIM ‐7 (His224/Arg228) structures, indicating a role of these residues in the substrate specificity.

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