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

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.