MANY OF THE CONSERVED NUCLEOTIDES OF TRNA(PHE) ARE NOT ESSENTIAL FOR TERNARY COMPLEX-FORMATION AND PEPTIDE ELONGATION

An RNase protection assay was used to show that the dissociation rate constants and equilibrium constants of unmodified yeast and Escherichi a coli phenylalanyl-tRNA(Phe)s to elongation factor Tu from E. coli we re very similar to each other and to their fully modified counterparts . The affinity of aminoacylated tRNA to elongation factor Tu was subst antially lower when GTP analogues were used in place of GTP, emphasizi ng the importance of the beta-gamma phosphate linkage in the function of G-proteins. Fourteen different mutations in conserved and semi-cons erved nucleotides of yeast phenylalanyl-tRNA(Phe) were tested for bind ing to elongation factor Tu.GTP and assayed for activity in the riboso mal A- and P-sites. Most of the mutations did not severely impair the function of these tRNAs in any of the assays. This suggests that the t ranslational machinery does not form sequence-specific interactions wi th the conserved nucleotides of tRNA.