Crystallization and preliminary X-ray crystallographic studies of recombinant thermoresistant gluconate kinase GntK from Escherichia coli

The thermoresistant gluconate kinase GntK from Escherichia coli, an essential enzyme in gluconate metabolism, has been expressed, purified and crystallized. For crystallization, the hanging-drop vapour-diffusion method was used with polyethylene glycol (PEG) 6000 and lithium chloride as precipitants. Three crystal forms belonging to the monoclinic space group C2 or the orthorhombic space groups P2(1)2(1)2(1) and P2(1)2(1)2 were obtained. The unit-cell parameters are a = 75.0, b = 79.3, c = 70.2 Angstrom, beta = 105.3 degrees (C2), a = 52.0, b = 79.3, c = 89.8 Angstrom (P2(1)2(1)2(1)) and a = 70.1, b = 74.1, c = 78.9 Angstrom (P2(1)2(1)2). In all three crystal forms, there are two molecules in the asymmetric unit; the different forms occur in the same crystallization drop. The crystals diffract to at least 2.0 Angstrom using synchrotron radiation.