6.3.2.13 computational docking of inhibitors to crystal structure. Uracil recognition site is a probable binding site for quinolone inhibitors 6.3.2.13 crystals of native and selenomethionine MurE are grown in the presence of UDP-N-acetylmuramoyl-L-alanyl-D-glutamate, 0.002 ml of protein solution containing 10 mg/ml enzyme, 20 mM HEPES, pH 7.5 200 mM NaCl, 5 mM dithiothreitol and 1 mM UDP-N-acetylmuramoyl-L-alanyl-D-glutamate, are equilibrated together with 0.002 ml reservoir buffer consisting of 100 mM HEPES, pH 7.5, 13% polyethylene glycol monomethyl ether 5000, 500 mM LiCl, 10% isopropanol and 5 mM dithiothreitol, against 1 ml reservoir buffer, crystals diffract to 2.0 A 6.3.2.13 modeling of the threedimensional structure using comparative modeling methods based on the X-ray crystal structure of MurE from Escherichia coli. The 3D-structure was docked with its substrates meso-diaminopimelic acid and UDP-N-acetylmuramoyl-glycyl-D-glutamate and its product UDP-N-acetyl muramoyl-glycyl-D-Glu-meso-diaminopimelate and also with ATP. The carboxylic acid group of UDP-N-acetylmuramoyl-glycyl-D-glutamate is positioned in proximity to gamma-phosphate of the ATP to facilitate the formation of acylphosphate intermediate. The orientation of an amino group of diaminopimelate facilitates the nucleophilic attack to form the product 6.3.2.13 to 3.0 A resolution in the presence of the substrate UDP-MurNAc-L-Ala-D-Glu. Protein consists of 3 domains consisting of residues 25-139,140-378 and 379-535, respectively. The UAG ligand binds to both domains 1 and 2 with the UDP portion binding to domain 1 and the peptide to domain 2. The substrate molecule UAG is bound between domains 1 and 2