D-Tyrosyl-tRNA(Tyr) metabolism in Saccharomyces cerevisiae

The Saccharomyces cerevisiae YDL219w (DTD1) gene, which codes for an amino acid sequence sharing 34% identity with the Escherichia coli D-Tyr-tRNA(Tyr ) deacylase, was cloned, and its product was functionally characterized. Ov erexpression in the yeast of the DTD1 gene from a multicopy plasmid increas ed D-Tyr-tRNA(Tyr) deacylase activity in crude extracts by two orders of ma gnitude. Upon disruption of the chromosomal gene, deacylase activity was de creased by more than 90%, and the sensitivity to D-tyrosine of the growth o f S. cerevisiae was exacerbated. The toxicity of D-tyrosine was also enhanc ed under conditions of nitrogen starvation, which stimulate the uptake of D -amino acids. In relation with these behaviors, the capacity of purified S. cerevisiae tyrosyl-tRNA synthetase to produce D-Tyr-tRNA(Tyr) could be sho wn. Finally, the phylogenetic distribution of genes homologous to DTD1 was examined in connection with L-tyrosine prototrophy or auxotrophy. In the au xotrophs, DTD1-like genes are systematically absent. In the prototrophs, th e putative occurrence of a deacylase is variable. It possibly depends on th e L-tyrosine anabolic pathway adopted by the cell.