Abstract
The glycyl-tRNA synthetase from Thermus thermophilus is a dimer of molecular mass 115 kDa, which has been crystallised using the vapour diffusion method from 5 to 7% polyethylene glycol 6000, 0.8 to 1.4 M NaCl at protein concentrations of 2 to 8 mg/ml. Nucleation is carried out at 4 degree C and crystals are subsequently transferred to 15 degree C to maximise growth. Crystals are truncated rhombohedra measuring on average 0.4 mm x 0.4 mm x 0.2 mm, which appear within a few days and reach full size in one to two months. GlyRS crystallises in two closely related space groups, P2 sub(1)2 sub(1)2 sub(1) and C2,2,2 sub(1), both with the same cell a = 125 angstrom, b = 254 angstrom, c = 104 angstrom. Crystal packing in P2 sub(1)2 sub(1)2 sub(1) is strongly C-centered. The crystals have V sub(M) = 3.6 angstrom super(3)/Da and a solvent content of 61%, with one dimer in the asymmetric unit in C2,2,2 sub(1) and two dimers in P2 sub(1)2 sub(1)2 sub(1). The best native data extend to 2.9 angstrom in C2,2,2 sub(1) and are 90.6% complete with an R-factor between symmetry-related reflections of 10.0%. The structure has been solved by multiple isomorphous replacement and model building is in progress.