Crystallization of Thermus thermophilus histidyl-tRNA synthetase and its complex with tRNAHis

Histidyl-tRNA synthetase (HisRS) has been purified from the extreme thermophile Thermus thermophilus. The protein has been crystallized separately with histidine and with its cognate tRNAHis. Both crystals have been obtained using the vapor diffusion method with ammonium sulphate as precipitant. The crystals of HisRS with histidine belong to the spacegroup P2(1)2(1)2 with cell parameters a = 171.3 A, b = 214.7 A, c = 49.3 A, alpha = beta = gamma = 90 degrees. A complete data set to a resolution of 2.7A with an Rmerge on intensities of 4.1% has been collected on a single frozen crystal. A partial data set collected on a crystal of HisRS in complex with tRNAHis shows that the crystals are tetragonal with cell parameters a = b = 232 A, c = 559 A, alpha = beta = gamma = 90 degrees and diffract to about 4.5 A resolution.