A Chinese hamster ovary leucyl-tRNA synthetase mutant with a uniquely altered high molecular weight leucyl-tRNA synthetase complex

摘要

The Chinese hamster ovary (CHO) cell culture temperature-sensitive mutant ts 025Cl with a defect in leucyl-tRNA synthetase (LeuRS) does not have an inherently more thermolabile LeuRS, but instead the mutation causes the complete loss of the LeuRS high molecular weight complexes which are present in normal wild-type cells. The mutant cell LeuRS has a single 8 S enzyme form which corresponds hydrodynamically to the 8 S free form of wild-type enzyme. Both 8 S forms have the same thermostability and the same K m for leucine, indicating that there is no inherent defect in the catalytic activity of the enzyme. The temperature-sensitive phenotype can be explained by the lack of thermostable high molecular weight forms of LeuRS.