A complex from cultured Chinese hamster ovary cells containing nine aminoacyl‐tRNA synthetases

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Abstract
The size distribution of the 20 aminoacyl‐tRNA synthetses from wild‐type Chinese hamster ovary (CHO) cells and from the mutant cell line tsH1, containing a temperature‐sensitive leucyl‐tRNA synthetase, was determined by gel filtration. Nine aminoacyl‐tRNA synthetases, specific for arginine, aspartic acid, glutamic acid, glutamine, isoleucine, leucine, lysine, methionine and proline, which coeluted as high‐Mr entities (Mr∼ 1.2 × 106), were further co‐purified to yield a multienzyme complex, the polypeptide composition of which was identical to that previously determined for the complex from rabbit liver. Immunoprecipitates obtained from crude extracts of wild‐type and tsH1 mutant cells, using specific antibodies directed to the lysyl‐tRNA or methionyl‐tRNA synthetase components of the complex, displayed the same polypeptide compositions as that of the purified complex, thereby establishing the heterotypic nature of this complex. Although the activity of leucyl‐tRNA synthetase from the mutant cells, grown at a permissive temperature, was low compared to that from the wild‐type, the polypeptide of Mr 129000, corresponding to this enzyme, was present in similar amounts and occurred exclusively as a component of the high‐Mr complex. Finally, we report that attempts to demonstrate phosphorylation of the components of the complex from cultured CHO, HeLa and C3 cells were unsuccessful.