Potential for Interdependent Development of tRNA Determinants for Aminoacylation and Ribosome Decoding

Although the nucleotides in tRNA required for aminoacylation are conserved in evolution, bacterial aminoacyl-tRNA synthetases (aaRSs) are unable to acylate eukaryotic tRNA. The cross-species barrier may be due to the absence of eukaryote-specific domains from bacterial aaRSs. Here we show that while E. coli CysRS cannot acylate human tRNA(Cys), the fusion of a eukaryote-specific domain of human CysRS overcomes the cross-species barrier in human tRNA(Cys). In addition to enabling recognition of the sequence differences in the tertiary core of tRNA(Cys), the fused eukaryotic domain redirects the specificity of E. coli CysRS from the A37 present in bacterial tRNA(Cys) to the G37 in mammals. Further experiments show that the accuracy of codon recognition on the ribosome was also highly sensitive to the A37-to-G37 transition in tRNA(Cys). These results raise the possibility of the development of tRNA nucleotide determinants for aminoacylation being interdependent with those for ribosome decoding.