A NEW CRYSTAL FORM OF THE COMPLEX BETWEEN SERYL-TRANSFER RNA-SYNTHETASE AND TRANSFER RNA(SER) FROM THERMUS-THERMOPHILUS THAT DIFFRACTS TO 2.8-ANGSTROM RESOLUTION

Two distinct complexes between seryl-tRNA synthetase and tRNA(Ser) from Thermus thermophilus have been crystallized using ammonium sulphate as a precipitant. Form III crystals grow from solutions containing a 1:2.5 stoichiometry of synthetase dimer to tRNA. They are of monoclinic space group C2 with unit cell dimensions a = 211.6 angstrom, b = 126.8 angstrom, c = 197.1 angstrom, beta = 132.4-degrees and diffract to about 3.5 angstrom. Preliminary crystallographic results show that the crystallographic asymmetric unit contains two synthetase dimers. Form IV crystals grow from solutions containing a 1:1.5 stoichiometry of synthetase dimer to tRNA. They are of orthorhombic space group P2(1)2(1)2(1) with unit cell dimensions a = 124.5 angstrom, b = 128.9 angstrom, c = 121.2 angstrom and diffract to 2.8 angstrom resolution. Preliminary crystallographic results show that these crystals contain only one tRNA molecule bound to a synthetase dimer.