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

Crystals of the complex between seryl-tRNA synthetase and tRNA2ser fro m 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 d erivative and solvent flattening was used to produce a map at 4 angstr om resolution. This shows that a tRNA molecule binds across the dimer, the anticodon stem and loop do not contact the protein and the helica l arm of the enzyme contacts the TPSIC loop and the long extra arm of the tRNA.