2.7.1.148 AaIspE is crystallized by vapor diffusion. Ordered and reproducible crystals of AaIspE are obtained and multiple-wavelength anomalous dispersion methods are applied to obtain the initial phases. 3 medium-resolution complex crystal structures are determined. The crystals are isomorphous with two molecules in the asymmetric unit. 686699 2.7.1.148 free enzyme, in complex with substrates 4-(cytidine 5'-diphospho)-2-C-methyl-D-erythritol, ADP and with adenyl imidodiphosphate, to 1.0, 1.54, 1.0, and 1.0 A resolution, respectively. The structures present a characteristic galactose/homoserine/mevalonate/phosphomevalonate kinase superfamily alpha/beta-fold with a catalytic center located in a cleft between two domains and display clear substrate and ATP binding pockets 722218 2.7.1.148 in complex with ADP, to 2.0 A resolution, and comparison with a monoclinic crystal form of a ternary complex of Escherichia coli 4-diphosphocytidyl-2C-methyl-D-erythritol kinase also with two molecules in the asymmetric unit. The molecular packing is different in the two forms. In the asymmetric unit of the triclinic crystal form the substrate-binding sites are occluded by structural elements of the partner, suggesting that the triclinic dimer is an artefact of the crystal lattice. The surface area of interaction in the triclinic form is almost double that observed in the monoclinic form 721187 2.7.1.148 purified recombinant enzyme in ternary complex with substrate and non-hydrolyzable ATP analogue adenosine 5'-[beta,gamma-imino]triphosphate, i.e. AMP-PNP, 25 mg/ml protein in 50 mM Tris-HCl, pH 7.7, 50 mM NaCl, 3 mM AMP-PNP, and 2 mM substrate 4-(cytidine 5'-phosphate)-2-C-methyl-D-erythritol, hanging drop vapour diffusion method, 0.001 ml protein solution mixed with equal volume of reservoir solution containing 20% polyethylene glycol 8000, 0.2 M magnesium acetate, 0.1 M sodium cacodylate, pH 6.5, and 0.0002 ml of 0.25 sulfo-betaine, cryoprotection at -173°C by 20% glycerol, X-ray diffraction structure determination and analysis at 2.0 A resolution 663207 2.7.1.148 purified recombinant selenomethionine-labeled enzyme, hanging drop vapour diffusion method, 20°C, 0.002 ml protein solution containing 2.2 mg/ml protein, 20 ml Tris-HCl, pH 8.0, and 50 mM NaCl, are mixed with 0.001 ml mother liquor containing 33 mM Tris-HCl, pH 8.5, 67 mM sodium acetate, 13% isopropanol, 8% butanol, and 13% PEG 4000, cryoprotection at -173°C in 30% glycerol, X-ray diffraction structure determination and analysis at 1.7 A resolution 662149 2.7.1.148 structure-activity relationship studies with inhibitors 6-(benzylsulfanyl)-2-(2-hydroxyphenyl)-4-oxo-3,4-dihydro-2H-1,3-thiazine-5-carbonitrile and (4E)-3-methyl-4-[(5-phenylfuran-2-yl)methylidene]-1,2-oxazol-5(4H)-one 721831 2.7.1.148 the structure is resolved by X-ray diffraction at a resolution of 2.01 A 699633