Purification and Properties of Alanyl-tRNA Synthetase from Bombyx mori: A Monomeric Enzyme1

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Abstract
Alanyl-tRNA synthetase was purified from the posterior silk glands of Bombyx mori by ammonium sulfate fractionation and chromatography on DEAE-Sephacel and hydroxyapatite columns. The yield was about 100 mg of the enzyme per 1 kg of the glands. The enzyme required both L-alanine and alanine tRNA for pyrophosphate formation from ATP. The PP1 formation was observed even after tRNA was fully aminoacylated. The enzyme was found to be a monomer of 115K daltons by SDS-polyacrylamide gel electrophoresis, gel filtration and suberimidate cross-linking experiments. The monomeric enzyme did not dimerize in the presence of the alanine tRNA. The enzyme and the tRNA formed a 1 : 1 complex. The results indicated that Bombyx mori alanyl-tRNA synthetase functions in a monomeric state.