Purification of Tyrosine: tRNA Ligase from Saccharomyces cerevisiae αS288C

Abstract

L-Tyrosine: tRNA ligase (AMP)[EC 6. 1. 1. 1] has been purifeed te homogeneity from a genetically well-characterized, haploid strain of yeast, Saccharomyces cerevisiae α S288C. The kinetic constants for tRNA^Tyr are: K_m=3.5×10^-7; k_cat=365 min^-1. Under dissociating conditions, the enzyme gives a single band on discontinuous gel electrophoresis, corresponding to a molecular weight=31, 500. Under non-dissociating conditions, where the activity of the enzyme is retained, the molecular weight estimated by gel filtration is 116, 000. Though tentative, these data indicate this enzyme may be composed of four subunits.