Kinetic and spectroscopic characterization of native and metal‐substituted β‐lactamase from Aeromonas hydrophila AE036

Abstract
Two metal ion binding sites are conserved in metallo‐β‐lactamase from Aeromonas hydrophila. The ligands of a first zinc ion bound with picomolar dissociation constant were identified by EXAFS spectroscopy as one Cys, two His and one additional N/O donor. Sulfur‐to‐metal charge transfer bands are observed for all mono‐ and di‐metal species substituted with Cu(II) or Co(II) due to ligation of the single conserved cysteine residue. Binding of a second metal ion results in non‐competitive inhibition which might be explained by an alternative kinetic mechanism. A possible partition of metal ions between the two binding sites is discussed.

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