1mbl | pdb_00001mbl

A catalytically-impaired class A beta-lactamase: 2 Angstroms crystal structure and kinetics of the Bacillus licheniformis E166A mutant

spinqualitylabelsall models 1mbl, resolution 2.00Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1mbl is a 2 chain structure with sequence from "clostridium_licheniforme"_weigmann_1898 "clostridium licheniforme" weigmann 1898. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: SO4 Activity: Beta-lactamase, with EC number 3.5.2.6 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed In the beta-lactamase (penicillinase) of Bacillus licheniformis 749/C, site specific mutation of Glu166 to Ala caused a million-fold reduction of catalytic activity towards both penicillin and cephalosporin substrates and resulted in the stoichiometric accumulation of the acyl enzyme. The rate of deacylation generally slowed by as much as 10(-7) compared to the wild type. The acyl enzyme intermediate was observed by HPLC, but not by X-ray diffraction. The mutant was crystallized from methoxyPEG 5000 at pH 6.2 in space group P2(1) with Z = 4. Molecular replacement based on the wild type structure followed by refinement produced an R factor of 17.2% for 25,800 3 sigma data from 10 to 2 A. Deviations from bond and angle ideals are 0.005 A and 1.5 degrees respectively. The mutant differs very little from the wild type structure, with only 0.25 A (r.m.s.) differences in backbone atoms; the CD spectra and thermal stabilities of the two enzymes are identical. Changes in the positions of the reactive Ser70 and conserved Lys73 are not significant, suggesting that the proposed salt linkage to Glu166 in the wild type enzyme is weak or non-existent. The calculated solvent exposure of Ser70 and Lys73 increases slightly and a buried water molecule is now positioned near Lys73. The hydrolytic water seen in the native active site shifts markedly by 1.6 A, but is held in the active site by Asn170, which possibly becomes an ineffective substitute for Glu166 in activating the water for deacylation. A catalytically-impaired class A beta-lactamase: 2 A crystal structure and kinetics of the Bacillus licheniformis E166A mutant.,Knox JR, Moews PC, Escobar WA, Fink AL Protein Eng. 1993 Jan;6(1):11-8. PMID:8433965 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Beta-lactamase

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