3m6b

Crystal Structure of the Ertapenem Pre-isomerized Covalent Adduct with TB B-lactamase

spinqualitylabelsall models 3m6b, resolution 1.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3m6b is a 1 chain structure with sequence from Mycobacterium tuberculosis. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.3Å Ligands: 1RG, PO4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function BLAC_MYCTU 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 Despite the enormous success of beta-lactams as broad-spectrum antibacterials, they have never been widely used for the treatment of tuberculosis (TB) due to intrinsic resistance that is caused by the presence of a chromosomally encoded gene (blaC) in Mycobacterium tuberculosis. Our previous studies of TB BlaC revealed that this enzyme is an extremely broad-spectrum beta-lactamase hydrolyzing all beta-lactam classes. Carbapenems are slow substrates that acylate the enzyme but are only slowly deacylated and can therefore act also as potent inhibitors of BlaC. We conducted the in vitro characterization of doripenem and ertapenem with BlaC. A steady-state kinetic burst was observed with both compounds with magnitudes proportional to the concentration of BlaC used. The results provide apparent K(m) and k(cat) values of 0.18 muM and 0.016 min(-1) for doripenem and 0.18 muM and 0.017 min(-1) for ertapenem, respectively. FTICR mass spectrometry demonstrated that the doripenem and ertapenem acyl-enzyme complexes remain stable over a time period of 90 min. The BlaC-doripenem covalent complex obtained after a 90 min soak was determined to 2.2 A, while the BlaC-ertapenem complex obtained after a 90 min soak was determined to 2.0 A. The 1.3 A diffraction data from a 10 min ertapenem-soaked crystal revealed an isomerization occurring in the BlaC-ertapenem adduct in which the original Delta(2)-pyrroline ring was tautomerized to generate the Delta(1)-pyrroline ring. The isomerization leads to the flipping of the carbapenem hydroxyethyl group to hydrogen bond to carboxyl O2 of Glu166. The hydroxyethyl flip results in both the decreased basicity of Glu166 and a significant increase in the distance between carboxyl O2 of Glu166 and the catalytic water molecule, slowing hydrolysis. Biochemical and Structural Characterization of Mycobacterium tuberculosis beta-Lactamase with the Carbapenems Ertapenem and Doripenem.,Tremblay LW, Fan F, Blanchard JS Biochemistry. 2010 Apr 7. PMID:20353175 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Beta-lactamase 3D structures

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