The effect of chemical modification of the CCA end of yeast tRNAPhe on its biological activity on ribosomes.

Yeast tRNAPhe containing 2-thiocytidine (s2C) at position 75 was alkylated specifically at this residue. The biological activities of alkylated and native tRNAPhe were compared in an Escherichia coli protein-synthesizing system in vitro. The alkylated tRNAPhe proved to be active in all steps involved in the elongation phase but the rate of the peptide transfer reaction was somewhat lower when the alkylated tRNAPhe acted as an acceptor of peptidyl residues as compared to native tRNAPhe. These results raise the possibility for attaching spectroscopic or affinity labels at the s2C-75 residue of tRNAPhe without impairing the activity of the tRNA.