ALTERATIONS AT THE 3'-CCA END OF ESCHERICHIA-COLI AND THERMUS-THERMOPHILUS TRNA(PHE) DO NOT ABOLISH THEIR ACCEPTOR ACTIVITY

The 3'-CCA end of tRNA(Phe) from Escherichia coli and Thermus thermoph ilus was changed to AAA, CCC, UUU and UUA by the stepwise degradation procedure of the 3'-CCA end of tRNA(Phe) followed by the ligation with oligoribotrinucleotides. Substrate activity of tRNA(UUA)(Phe) and tRN A(CCC)(Phe) in tRNA aminoacylation was shown. tRNA(AAA)(Phe) is a bad substrate for E. coli and Til. thermophilus phenylalanyl-tRNA syntheta ses. tRNA(UUU)(Phe) has no detectable activity in tRNA aminoacylation. Therefore the nature of the 3'-end of tRNA(Phe) plays an important ro le in tRNA binding and its substrate efficiency. Nevertheless the CCA sequence at the 3'-end of tRNA(Phe) does not seem to be an absolute re quirement for tRNA aminoacylation.