Role of modified nucleosides in tRNA: Effect of modification of the 2-thiouridine derivative located at the 5'-end of the anticodon of yeast transfer RNA2Lys

Yeast tRNA Lys2 codes preferentially for AAA and contains a 2-thiouridine derivative (U) at the 5'-position of the anticodon. Removal of the 2-thio group from U by treatment with CNBr did not affect the amino acid accepting activity of the modified tRNA Lys2. CNBr treated tRNA Lys2 was active in protein synthesis but with a much reduced efficiency. Although the modified tRNA Lys2 was recognized by elongation factor (EF) T, the EFT dependent binding to ribosomes to tRNA Lys2 (CNBr) was markedly decreased.