3znb
From Proteopedia
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| - | | | + | {{STRUCTURE_3znb| PDB=3znb | SCENE= }} |
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'''METALLO-BETA-LACTAMASE (ZN, HG-BOUND FORM)''' | '''METALLO-BETA-LACTAMASE (ZN, HG-BOUND FORM)''' | ||
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[[Category: Concha, N O.]] | [[Category: Concha, N O.]] | ||
[[Category: Herzberg, O.]] | [[Category: Herzberg, O.]] | ||
| - | [[Category: | + | [[Category: Beta-lactamase]] |
| - | [[Category: | + | [[Category: Hydrolase]] |
| - | [[Category: | + | [[Category: Mercury]] |
| - | [[Category: | + | [[Category: Metallo beta-lactamase]] |
| - | [[Category: | + | [[Category: Zinc]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 22:15:51 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 19:15, 4 May 2008
METALLO-BETA-LACTAMASE (ZN, HG-BOUND FORM)
Overview
The metallo-beta-lactamases require zinc or cadmium for hydrolyzing beta-lactam antibiotics and are inhibited by mercurial compounds. To data, there are no clinically useful inhibitors of this class of enzymes. The crystal structure of the Zn(2+)-bound enzyme from Bacteroides fragilis contains a binuclear zinc center in the active site. A hydroxide, coordinated to both zinc atoms, is proposed as the moiety that mounts the nucleophilic attack on the carbonyl carbon atom of the beta-lactam ring. To study the metal coordination further, the crystal structures of a Cd(2+)-bound enzyme and of an Hg(2+)-soaked zinc-containing enzyme have been determined at 2.1 A and 2.7 A, respectively. Given the diffraction resolution, the Cd(2+)-bound enzyme exhibits the same active-site architecture as that of the Zn(2+)-bound enzyme, consistent with the fact that both forms are enzymatically active. The 10-fold reduction in activity of the Cd(2+)-bound molecule compared with the Zn(2+)-bound enzyme is attributed to fine differences in the charge distribution due to the difference in the ionic radii of the two metals. In contrast, in the Hg(2+)-bound structure, one of the zinc ions, Zn2, was ejected, and the other zinc ion, Zn1, remained in the same site as in the 2-Zn(2+)-bound structure. Instead of the ejected zinc, a mercury ion binds between Cys 104 and Cys 181, 4.8 A away from Zn1 and 3.9 A away from the site where Zn2 is located in the 2-Zn(2+)-bound molecule. The perturbed binuclear metal cluster explains the inactivation of the enzyme by mercury compounds.
About this Structure
3ZNB is a Single protein structure of sequence from Bacteroides fragilis. Full crystallographic information is available from OCA.
Reference
Crystal structures of the cadmium- and mercury-substituted metallo-beta-lactamase from Bacteroides fragilis., Concha NO, Rasmussen BA, Bush K, Herzberg O, Protein Sci. 1997 Dec;6(12):2671-6. PMID:9416622 Page seeded by OCA on Sun May 4 22:15:51 2008
