Differential Binding of Co(II) and Zn(II) to Metallo-beta-Lactamase Bla2 from Bacillus anthracis

Department of Chemistry and Biochemistry, 160 Hughes Hall, Miami University, Oxford, Ohio 45056, USA.
Journal of the American Chemical Society (Impact Factor: 11.44). 08/2009; 131(30):10753-62. DOI: 10.1021/ja900296u
Source: PubMed

ABSTRACT In an effort to probe the structure, mechanism, and biochemical properties of metallo-beta-lactamase Bla2 from Bacillus anthracis, the enzyme was overexpressed, purified, and characterized. Metal analyses demonstrated that recombinant Bla2 tightly binds 1 equiv of Zn(II). Steady-state kinetic studies showed that mono-Zn(II) Bla2 (1Zn-Bla2) is active, while di-Zn(II) Bla2 (ZnZn-Bla2) was unstable. Catalytically, 1Zn-Bla2 behaves like the related enzymes CcrA and L1. In contrast, di-Co(II) Bla2 (CoCo-Bla2) is substantially more active than the mono-Co(II) analogue. Rapid kinetics and UV-vis, (1)H NMR, EPR, and EXAFS spectroscopic studies show that Co(II) binding to Bla2 is distributed, while EXAFS shows that Zn(II) binding is sequential. To our knowledge, this is the first documented example of a Zn enzyme that binds Co(II) and Zn(II) via distinct mechanisms, underscoring the need to demonstrate transferability when extrapolating results on Co(II)-substituted proteins to the native Zn(II)-containing forms.

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