Crystallization and preliminary crystallographic analysis of 2-keto-3-deoxygluconate kinase from Thermus thermophilus

2-Keto-3-deoxygluconate kinase (KDGK) catalyzes the phosphorylation of 2-keto-3-deoxygluconate (KDG) to 2-keto-3-deoxy-6-phosphogluconate. Two crystal forms of KDGK from Thermus thermophilus were obtained by vapour-diffusion and microbatch methods. Crystals in the form of triangular plates (TtKDGK-1) were obtained that belong to space group P3, with unit-cell parameters a = b = 145.83, c = 74.63 Å, and diffract to 3.2 Å. These crystals exhibited nearly perfect hemihedral twinning. Assigning six subunits of TtKDGK to the asymmetric unit of the crystal corresponds to a 46.2% solvent content. A single plate-like crystal (TtKDGK-2) belonged to space group P6₃, with unit-cell parameters a = b = 84.83, c = 168.49 Å, and diffracts to 2.25 Å. This crystal exhibits only partial hemihedral twinning, with a twin fraction of 24.4%. Diffraction-quality crystals of TtKDGK with bound ATP (TtKDGK-ATP), a = b = 84.72, c = 321.61 Å and with bound KDG plus the ATP analogue AMP-PNP (TtKDGK-ATP-KDG), with unit-cell parameters a = b = 84.32, c = 168.7 Å, were also prepared and characterized.