The Complex Formation between Escherichia coli Aminoacyl‐tRNA, Elongation Factor Tu and GTP

Abstract

The interaction between Escherichia coli aminoacyl‐tRNAs and elongation factor Tu (EF‐Tu) · GTP was examined. Ternary complex formation with Phe‐tRNA^Phe and Lys‐tRNA^Lys was compared to that with the respective misaminoacylated Tyr‐tRNA^Phe and Phe‐tRNA^Lys. There was no pronounced difference in the efficiency of aminoacyl‐tRNA · EF‐Tu · GTP complex formation between Phe‐tRNA^Phe and Tyr‐tRNA^Phe. However, Phe‐tRNA^Lys was bound preferentially to EF‐Tu · GTP as compared to Lys‐tRNA^Lys. This was shown by the ability of EF‐Tu · GTP to prevent the hydrolysis of the aminoacyl ester linkage of the aminoacyl‐tRNA species. Furthermore, gel filtration of ternary complexes revealed that the complex formed with the misaminoacylated tRNA^LyS was also more stable than the one formed with the correctly aminoacylated tRNA^Lys. Both misaminoacylated aminoacyl‐tRNA species could participate in the ribosomal peptide elongation reaction. Poly(U)‐directed synthesis of poly(Tyr) using Tyr‐tRNA^Phe occurred to a comparable extent as the synthesis of poly(Phe) with Phe‐tRNA^Phe. In the translation of poly(A) using native Lys‐tRNA^Lys, poly(Lys) reached a lower level than poly(Phe) when Phe‐tRNA^LyS was used. It is concluded that the side‐chain of the amino acid linked to a tRNA affects the efficiency of the aminoacyl‐tRNA · EF‐Tu · GTP ternary complex formation.