Spectroscopic and mechanistic studies of heterodimetallic forms of metallo-β-lactamase NDM-1.


In an effort to characterize the roles of each metal ion in metallo-β-lactamase NDM-1, heterodimetallic analogues (CoCo-, ZnCo-, and CoCd-) of the enzyme were generated and characterized. UV-vis, (1)H NMR, EPR, and EXAFS spectroscopies were used to confirm the fidelity of the metal substitutions, including the presence of a homogeneous, heterodimetallic cluster, with a single-atom bridge. This marks the first preparation of a metallo-β-lactamase selectively substituted with a paramagnetic metal ion, Co(II), either in the Zn1 (CoCd-NDM-1) or in the Zn2 site (ZnCo-NDM-1), as well as both (CoCo-NDM-1). We then used these metal-substituted forms of the enzyme to probe the reaction mechanism, using steady-state and stopped-flow kinetics, stopped-flow fluorescence, and rapid-freeze-quench EPR. Both metal sites show significant effects on the kinetic constants, and both paramagnetic variants (CoCd- and ZnCo-NDM-1) showed significant structural changes on reaction with substrate. These changes are discussed in terms of a minimal kinetic mechanism that incorporates all of the data.


Yang, Hao; Aitha, Mahesh; Marts, Amy R; Hetrick, Alyssa; Bennett, Brian; Crowder, Michael W; Tierney, David L;


  • Electron Spin Resonance Spectroscopy
  • Magnetic Resonance Spectroscopy
  • Spectrophotometry, Ultraviolet
  • X-Ray Absorption Spectroscopy
  • beta-Lactamases/ chemistry
  • beta-Lactamases/ metabolism

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