THE MULTIENZYME COMPLEX CONTAINING 9 AMINOACYL-TRANSFER-RNA SYNTHETASES IS UBIQUITOUS FROM DROSOPHILA TO MAMMALS

In all mammalian cells studied so far, a multienzyme complex containin g the nine aminoacyl-tRNA synthetases specific for the amino acids Glu , Pro, Ile, Leu, Met, Gin, Lys, Arg and Asp was characterized. The com plexes purified from various sources display very similar polypeptide compositions; they are composed of 11 polypeptides with molecular mass es ranging from 18 to 150 kDa. By contrast, the corresponding enzymes from prokaryotes and lower eukaryotes behave as free enzymes. In order to test for the ubiquity of the multisynthetase complex in all metazo an species, we have searched for a similar complex in Drosophila. We h ave purified to homogeneity, from Schneider cells, a high molecular we ight complex comprising the same nine synthetase activities. Its polyp eptide composition resembles that of the complexes isolated from mamma lian sources. By using the Western blotting procedure, some of the con stituent polypeptides of the Drosophila complex were assigned to speci fic aminoacyl-tRNA synthetases. These findings support the proposal ac cording to which the multisynthetase complex is an idiosyncratic featu re of all higher eukaryotic cells.