Discriminator base of tRNA Asp is involved in amino acid acceptor activity

Abstract

Unmodified E. coli tRNA Asp was obtained by in vitro transcription with T7 RNA polymerase from a plasmid carrying a tRNA Asp sequence adjacent to the T7 promoter. The transcript exhibited almost the same level of amino acid acceptor activity as intact tRNA Asp, and the kinetic parameters were also similar. However, substitution of the discriminator base (the fourth base from the 3′-end) markedly affected the amino acid acceptor activity. These results suggest that the discriminator base in tRNA Asp plays an important role in the recognition of aspartyl-tRNA synthetase.