Expression, purification and preliminary X-ray characterization of CTP synthetas...

A recombinant form of the CTP synthetase from Thermus thermophilus HB8 (tCTPs) was grown as colourless crystals by the hanging-drop vapour-diffusion technique using ammonium sulfate or sodium citrate as a precipitating agent. The crystals belong to space group I222, with unit-cell parameters a = 88.2, b = 118.9, c = 142.7 A, alpha = beta = gamma = 90 degrees, and are most likely to contain a monomer in the asymmetric unit with a V(M) value of 3.07 A(3) Da(-1). The crystals obtained from ammonium sulfate and sodium citrate solutions diffract X-rays to a resolution of 2.25 A using synchrotron X-ray sources and to a resolution of 2.35 A using Cu Kalpha X-rays from a rotating-anode generator.