tRNA residues evolved to promote translational accuracy

The decoding properties of 22 structurally conservative base-pair and base-triple mutations in the anticodon hairpin and tertiary core of Escherichia coli tRNA^Ala_GGC were determined under single turnover conditions using E. coli ribosomes. While all of the mutations were able to efficiently decode the cognate GCC codon, many showed substantial misreading of near-cognate GUC or ACC codons. Although all the misreading mutations were present in the sequences of other E. coli tRNAs, they were never found among bacterial tRNA^Ala_GGC sequences. This suggests that the sequences of bacterial tRNA^Ala_GGC have evolved to avoid reading incorrect codons.