Identity determinants of E. coli tRNA(Val).

In order to study the identity elements of valine tRNA, various transcripts of E. coli valine tRNA mutants were constructed. Both mutations at the second letter A35 of the anticodon and at the discriminator base A73 seriously damaged valine charging activity. Mutations at either the G3-C70 or U4-A69 base pairs in the acceptor stem also affected the activity. Only one nucleotide substitution of the second letter G35 of the anticodon with A35 brought an 18% valine charging activity into alanine tRNA, which acquired an almost full charging activity with valine by introducing an additional change at those two base pairs in the acceptor stem. These results indicate that the second letter A35 of the anticodon, discriminator base and acceptor stem are involved in recognition by valyl-tRNA synthetase.