1cef: Difference between revisions

Two clinically-important beta-lactam antibiotics, cephalothin and, cefotaxime, have been observed by X-ray crystallography bound to the, reactive Ser62 of the D-alanyl-D-alanine carboxypeptidase/transpeptidase, of Streptomyces sp. R61. Refinement of the two crystal structures produced, R factors for 3 sigma (F) data of 0.166 (to 1.8 A) and 0.170 (to 2.0 A), for the cephalothin and cefotaxime complexes, respectively. In each, complex, a water molecule is within 3.1 and 3.6 A of the acylated, beta-lactam carbonyl carbon atom, but is poorly activated by active site, residues for nucleophilic attack and deacylation. This apparent lack of, good stereochemistry for facile hydrolysis is in accord with the long, half-lives of cephalosporin intermediates in solution (20-40 h) and the, efficacy of these beta-lactams as inhibitors of bacterial cell wall, synthesis. Different hydrogen binding patterns of the two cephalosporins, to Thr301 are consistent with the low cefotaxime affinity of an altered, penicillin-binding protein, PBP-2x, reported in cefotaxime-resistant, strains of Streptococcus pneumoniae, and with the ability of mutant class, A beta-lactamases to hydrolyze third-generation cephalosporins.

1CEF is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Streptomyces_sp. Streptomyces sp.] with CEF as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Serine-type_D-Ala-D-Ala_carboxypeptidase Serine-type D-Ala-D-Ala carboxypeptidase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.4.16.4 3.4.16.4] Structure known Active Site: ACT. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1CEF OCA].  

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