CRYSTALLIZATION OF THE SERYL-TRANSFER RNA SYNTHETASE-TRANSFER RNA(SER) COMPLEX OF ESCHERICHIA-COLI

Crystals of the complex between seryl-tRNA synthetase and tRNA2ser from Escherichia coli have been obtained from ammonium sulphate solutions. The crystals are of the 1:2 enzyme:tRNA complex, belong to the space group C222(1), have cell dimensions of a = 128.9 angstrom, b = 164.9 angstrom, c = 127.3 angstrom and diffract anisotropically from 3.5 to 4.5 angstrom. An X-ray diffraction data set to 4 A has been collected. The combination of molecular replacement using the refined structure of the catalytic domain of the native enzyme, data from a heavy atom derivative and solvent flattening was used to produce a map at 4 angstrom resolution. This shows that a tRNA molecule binds across the dimer, the anticodon stem and loop do not contact the protein and the helical arm of the enzyme contacts the TPSIC loop and the long extra arm of the tRNA.