1bc2
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ZN-DEPENDENT METALLO-BETA-LACTAMASE FROM BACILLUS CEREUS
OverviewOverview
The structure of the zinc-dependent beta-lactamase II from Bacillus cereus, has been determined at 1.9 A resolution in a crystal form with two, molecules in the asymmetric unit and 400 waters (space group P3121; Rcryst, = 20.8%). The active site contains two zinc ions: Zn1 is tightly, coordinated by His86, His88, and His149, while Zn2 is loosely coordinated, by Asp90, Cys168, and His210. A water molecule (W1) lies between the two, zinc ions but is significantly closer to Zn1 and at a distance of only 1.9, A is effectively a hydroxide moiety and a potential, preactivated, nucleophile. In fact, Asp90 bridges W1 to Zn2, and its location is thus, distinct from that of the bridging water molecules in the binuclear zinc, peptidases or other binuclear zinc hydrolases. Modeling of penicillin, cephalosporin, and carbapenem binding shows that all are readily, accommodated within the shallow active site cleft of the enzyme, and the, Zn1-bound hydroxide is ideally located for nucleophilic attack at the, beta-lactam carbonyl. This enzyme also functions with only one zinc ion, present. The Zn1-Zn2 distances differ in the two independent molecules in, the crystal (3.9 and 4.4 A), yet the Zn1-W1 distances are both 1.9 A, arguing against involvement of Zn2 in W1 activation. The role of Zn2 is, unclear, but the B. cereus enzyme may be an evolutionary intermediate, between the mono- and bizinc metallo-beta-lactamases. The broad, specificity of this enzyme, together with the increasing prevalence of, zinc-dependent metallo-beta-lactamases, poses a real clinical threat, and, this structure provides a basis for understanding its mechanism and, designing inhibitors.
About this StructureAbout this Structure
1BC2 is a Single protein structure of sequence from Bacillus cereus with ZN and SO4 as ligands. Active as Beta-lactamase, with EC number 3.5.2.6 Known structural/functional Sites: , , and . Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of the zinc-dependent beta-lactamase from Bacillus cereus at 1.9 A resolution: binuclear active site with features of a mononuclear enzyme., Fabiane SM, Sohi MK, Wan T, Payne DJ, Bateson JH, Mitchell T, Sutton BJ, Biochemistry. 1998 Sep 8;37(36):12404-11. PMID:9730812
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