crystallization at 20Â°C by hanging-drop vapor diffusion from a 1:1 mixture of protein solution and reservoir solution [22%â28% polyethylene glycol MME 5000, 0.1 M MES (pH 6.5â7.0), and 0.2 M (NH4)2SO4]. Crystals grow in 7â10 days to an average size of 0.12 * 0.12 * 0.08 mM. The 2.1 A crystal structure of imidazole glycerol phosphate synthase reveals extensive interaction of the glutaminase and cyclase catalytic domains. At the domain interface, the glutaminase active site points into the bottomof the (beta/alpha)8 barrel of the cyclase domain. An ammonia tunnel through the (beta/alpha)8 barrel connects the glutaminase docking site at the bottom to the cyclase active site at the top. A conserved gate of four charged residues controls access to the tunnel
crystals are obtained by the hanging-drop vapor diffusion method at 20Â°C. Within two weeks, the crystals grow to full size (0.3 x 0.3 x 0.2 mm) in the space group P4(3)2(1)2 with unit cell parameters a = b = 82.2, c = 156.2 A. X-ray crystallographic study of the native enzyme at 2.3 A resolution
structures of a complex of the substrate N1-[(5'-phosphoribulosyl)formimino]-5-aminoimidazole-4-carboxamido-1-beta-D-ribofuranosyl 5'-phosphate and imidazole glycerol phosphate synthase covalently modified by the glutamine analogue acvicin at 2.5 A, apoenzyme at 2.4 A, and imidazole glycerol phosphate synthase inactivated by the glutamine analogue 6-diazo-5-oxo-L-norleucine at 2.5 A. Comparison of the free, acivicin-, and 6-diazo-5-oxo-L-norleucine-inactivated forms of the glutaminase active site reveals structural changes relevant to activation. The N1-[(5'-phosphoribulosyl)formimino]-5-aminoimidazole-4-carboxamido-1-beta-D-ribofuranosyl 5'-phosphate-bound and -free forms of the enzyme shed light on flexible parts of the molecule with potential roles in crosstalk between active sites
vapor diffusion method is used to obtain crystals with a rod-like morphology of a maximum size of about 0.4 x 0.2 x 0.2 mm3. Crystal structure of the heterodimeric bienzyme ImGP synthase comprising the glutaminase subunit HisH and the cyclase subunit HisF, at 2.4 A resolution.