BIOCHEMICAL CHARACTERIZATION OF A MUTANT ASPARAGINYL TRANSFER-RNA SYNTHETASE FROM CHINESE-HAMSTER OVARY CELLS

Abstract

The biochemical and physical properties of asparaginyl-tRNA synthetase from wild type Chinese hamster ovary cells and a temperature sensitive mutant strain (lys 65a) are compared. The asparaginyl-tRNA synthetase in the mutant strain exhibits a greater temperature lability in vitro, a higher temperature-independent Km for asparagine, and a lower temperature-dependent catalytic capacity than the enzyme from the wild type strain. The mutant enzyme shows no differences in its molecular weight, its Km for tRNAAsn, or its ability to aminoacylate tRNAAsn isoacceptor species compared to the wild type enzyme. These observations, as well as the growth properties of the mutant cells as a function of temperature and exogenous asparagine concentrations, are consistent with their decreased ability to aminoacylate tRNAAsn in vivo.