title: Isolation and characterization of two methionine: tRNA ligases from wheat germ.
abstract: Two methionine: tRNA ligases (here called ligase A and ligase B) with distinctly different enzymatic and molecular properties were isolated in homogenous form from extracts of raw wheat germ. Both the A and B enzyme are composed of single polypeptide chains of Mr 105000 and 70000 respectively. The smaller molecule (B) has been shown not to be a proteolytic fragment of the larger one (A). The catalytic properties of both the A and B enzymes have been established and the Mg2-dependent capacity to charge six purified methionine-accepting tRNAs have been compared to those of the methionine: tRNA ligases from Escherichia coli and bakers' yeast. The possible reasons for the presence of two methionine: tRNA ligases and their unusual monomeric nature are discussed.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000604:Amino Acyl-tRNA Synthetases / Q000302:isolation & purification; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008718:Methionine-tRNA Ligase / Q000302:isolation & purification / Q000378:metabolism; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D011487:Protein Conformation; D012639:Seeds / Q000201:enzymology*; D013045:Species Specificity; D014908:Triticum / Q000201:enzymology
chemical_list: D000596:Amino Acids; D007527:Isoenzymes; D010446:Peptide Fragments; D000604:Amino Acyl-tRNA Synthetases; D008718:Methionine-tRNA Ligase; D008274:Magnesium