COMPARATIVE-STUDY ON THE LOCATION OF TRYPTOPHANYL-TRANSFER-RNA SYNTHETASE AND COMPONENTS OF HIGH-MOLECULAR-WEIGHT AMINOACYL-TRANSFER-RNA SYNTHETASE COMPLEX IN MAMMALIAN-CELLS

The location of cytosolic tryptophanyl-tRNA synthetase (TrpRS), aminoa cyl-tRNA synthetases comprising the multienzyme high-molecular complex [glutamyl-tRNA synthetase (GluRS) and arginyl-tRNA synthetase (ArgRS) ], and polypeptides p37 and p43 of the multienzyme complex from rabbit kidney cells RK-1 grown in vitro was compared on ultrathin sections b y using immunogold. It was shown that the cellular distribution of Glu RS, ArgRS, and polypeptide p43 from the multienzyme complex and that o f TrpRS are practically similar. This allowed the suggestion that TrpR S in vivo is associated with the multienzyme complex and is easily rel eased upon cell lysis. The obtained data testify in favor of a multien zyme structure of the majority and probably all of the synthetases, at least in intact cells. Statistical analysis of the distribution of en zymes in various cell organelles showed that aminoacyl-tRNA synthetase s have a nonrandom compartmentalized distribution. In the nucleus amin oacyl-tRNA synthetases are found mainly in the vicinity of interchroma tin granules and regions of diffuse chromatin, and also at the border of compact and diffuse chromatin, and also at the border of compact an d diffuse chromatin, thus indicating that these enzymes may have addit ional functions. Detection of ArgRS and GluRS in the nucleus allows on e to suggest that either the multienzyme synthetase complexes are pres ent not only in the cytoplasm but also in the nucleus, or that the enz ymes dissociate from the complex and enter the nucleus as individual p roteins.