Crystallization of the seryl‐tRNA synthetase: tRNAser complex of Escherichia coli

Abstract

Crystals of the complex between seryl-tRNA synthetase and tRNA₂ ^ser 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,, have cell dimensions of a = 128.9 Å, b = 164.9 Å, c = 127.3 Å and diffract anisotropically from 3.5 to 4.5 Å. An X-ray diffraction data set to 4 Å 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 Å 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 TΨC loop and the long extra arm of the tRNA.