Crystallisation of the Glycyl-tRNA synthetase from thermus thermophilus and initial crystallographic data

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°C and crystals are subsequently transferred to 15°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, P2₁2₁2₁ and C2,2,2₁, both with the same cell a = 125 AÅ, b = 254 AÅ, c = 104 AÅ. Crystal packing in P2₁2₁2₁ is strongly C-centred. The crystals have V(M) = 3.6 Aų/Da and a solvent content of 61%, with one dimer in the asymmetric unit in C2,2,2₁ and two dimers in P2₁2₁2₁. The best native data extend to 2.9 AÅ in C2,2,2₁ 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.