Comparison of complexes containing lysyl-tRNA synthetase from normal and virus-transformed cells

Abstract

We compared the lysyl-tRNA synthetases from normal (Balb/3T3) and murine sarcoma virus-transformed (KA31) mouse fibroblasts. In agreement with several other reports of mammalian systems, the lysyl-tRNA synthetases from these cells occurred in very large postmicrosomal complexes as determined by gel filtration on agarose columns. Arginyl-, isoleucyl-, methionyl-, phenylalanyl-, and tyrosyl-tRNA synthetases also occurred as part of a large complex or complexes. Activity of glycyl- or leucyl-tRNA synthetase was not detected in a complex. The specific activities of arginyl- and methionyl-tRNA synthetases were three- and five-fold higher, respectively, in a complex from KA31 as compared with a complex from Balb/3T3. In contrast, the specific activity of lysyl-tRNA synthetase from the Balb/3T3 complex was 50% higher than that of the KA31 complex. tRNALys obtained from the complexes of Balb/3T3 and KA31 was fractionated into isoacceptors on columns of RPC-5. The relative amounts of lysine isoacceptors in total preparations of tRNA from normal whole cells and in tRNA obtained from the normal enzyme complex were the same. However, two isoacceptors were present in greater amounts and two were present in lesser amounts in the KA31 enzyme complex as compared with lysine isoacceptors in a total preparation of tRNA from KA31 cells.