4.2.2.18 | crystals are obtained at 20°C by hanging drop vapour-diffusion method using 0.1 M Na HEPES pH 7.5 buffer containing 1.5 M lithium sulfate as a precipitant. Crystals of the recombinant wild-type enzyme diffract to better than 1.5 A at -173°C. The crystals belong to space group R32, with unit-cell parameters a = b = 90.02 A, c = 229.82 A in the hexagonal axes. Selenomethionine-derivative crystals belong to a different space group, C2, with unit-cell parameters a = 159.32, cb = 91.92, c = 92.58 A, beta = 125.06. The C2 selenomethionine-derived crystal contains three molecules per asymmetric unit |