2uyx
From Proteopedia
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METALLO-BETA-LACTAMASE (1BC2) SINGLE POINT MUTANT D120S
Overview
Metallo-beta-lactamases are zinc-dependent hydrolases that inactivate, beta-lactam antibiotics, rendering bacteria resistant to them. Asp-120 is, fully conserved in all metallo-beta-lactamases and is central to, catalysis. Several roles have been proposed for Asp-120, but so far there, is no agreed consensus. We generated four site-specifically substituted, variants of the enzyme BcII from Bacillus cereus as follows: D120N, D120E, D120Q, and D120S. Replacement of Asp-120 by other residues with very, different metal ligating capabilities severely impairs the lactamase, activity without abolishing metal binding to the mutated site. A kinetic, study of these mutants indicates that Asp-120 is not the proton donor, nor, does it play an essential role in nucleophilic activation. Spectroscopic, and crystallographic analysis of D120S BcII, the least active mutant, bearing the weakest metal ligand in the series, reveals that this enzyme, is able to accommodate a dinuclear center and that perturbations in the, active site are limited to the Zn2 site. It is proposed that the role of, Asp-120 is to act as a strong Zn2 ligand, locating this ion optimally for, substrate binding, stabilization of the development of a partial negative, charge in the beta-lactam nitrogen, and protonation of this atom by a, zinc-bound water molecule.
About this Structure
2UYX is a Single protein structure of sequence from Bacillus cereus with ZN and GOL as ligands. Active as Beta-lactamase, with EC number 3.5.2.6 Structure known Active Site: AC1. Full crystallographic information is available from OCA.
Reference
Asp-120 locates Zn2 for optimal metallo-beta-lactamase activity., Llarrull LI, Fabiane SM, Kowalski JM, Bennett B, Sutton BJ, Vila AJ, J Biol Chem. 2007 Jun 22;282(25):18276-85. Epub 2007 Apr 10. PMID:17426028
Page seeded by OCA on Mon Nov 5 13:42:52 2007
