Crystal Structure of the Zinc-Dependent -Lactamase from Bacillus cereus at 1.9 Å Resolution: Binuclear A
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- 作者：Stella Maris Fabiane ; Maninder K. Sohi ; Tommy Wan ; David J. Payne ; John H. Bateson ; Tim Mitchell ; and Brian J. Sutton
- 刊名：Biochemistry
- 出版年：1998
- 出版时间：September 8, 1998
- 年：1998
- 卷：37
- 期：36
- 页码：12404 - 12411
- 全文大小：157K
- 年卷期：v.37,no.36(September 8, 1998)
- ISSN：1520-4995
文摘
The structure of the zinc-dependent 
-lactamase II from Bacillus cereus has been determinedat 1.9 Å resolution in a crystal form with two molecules in the asymmetric unit and 400 waters (spacegroup P3121; Rcryst = 20.8%). The active site contains two zinc ions: Zn1 is tightly coordinated byHis86, His88, and His149, while Zn2 is loosely coordinated by Asp90, Cys168, and His210. A watermolecule (W1) lies between the two zinc ions but is significantly closer to Zn1 and at a distance of only1.9 Å is effectively a hydroxide moiety and a potential, preactivated nucleophile. In fact, Asp90 bridgesW1 to Zn2, and its location is thus distinct from that of the bridging water molecules in the binuclear zincpeptidases or other binuclear zinc hydrolases. Modeling of penicillin, cephalosporin, and carbapenembinding shows that all are readily accommodated within the shallow active site cleft of the enzyme, andthe Zn1-bound hydroxide is ideally located for nucleophilic attack at the -lactam carbonyl. This enzymealso functions with only one zinc ion present. The Zn1-Zn2 distances differ in the two independentmolecules in the crystal (3.9 and 4.4 Å), yet the Zn1-W1 distances are both 1.9 Å, arguing againstinvolvement of Zn2 in W1 activation. The role of Zn2 is unclear, but the B. cereus enzyme may be anevolutionary intermediate between the mono- and bizinc metallo--lactamases. The broad specificity ofthis enzyme, together with the increasing prevalence of zinc-dependent metallo--lactamases, poses areal clinical threat, and this structure provides a basis for understanding its mechanism and designinginhibitors.
-lactamase II from Bacillus cereus has been determinedat 1.9 Å resolution in a crystal form with two molecules in the asymmetric unit and 400 waters (spacegroup P3121; Rcryst = 20.8%). The active site contains two zinc ions: Zn1 is tightly coordinated byHis86, His88, and His149, while Zn2 is loosely coordinated by Asp90, Cys168, and His210. A watermolecule (W1) lies between the two zinc ions but is significantly closer to Zn1 and at a distance of only1.9 Å is effectively a hydroxide moiety and a potential, preactivated nucleophile. In fact, Asp90 bridgesW1 to Zn2, and its location is thus distinct from that of the bridging water molecules in the binuclear zincpeptidases or other binuclear zinc hydrolases. Modeling of penicillin, cephalosporin, and carbapenembinding shows that all are readily accommodated within the shallow active site cleft of the enzyme, andthe Zn1-bound hydroxide is ideally located for nucleophilic attack at the -lactam carbonyl. This enzymealso functions with only one zinc ion present. The Zn1-Zn2 distances differ in the two independentmolecules in the crystal (3.9 and 4.4 Å), yet the Zn1-W1 distances are both 1.9 Å, arguing againstinvolvement of Zn2 in W1 activation. The role of Zn2 is unclear, but the B. cereus enzyme may be anevolutionary intermediate between the mono- and bizinc metallo--lactamases. The broad specificity ofthis enzyme, together with the increasing prevalence of zinc-dependent metallo--lactamases, poses areal clinical threat, and this structure provides a basis for understanding its mechanism and designinginhibitors.