Quantifying mistranslation from alanine tRNA anticodon variants in S. cerevisiae

Transfer RNAs (tRNAs) maintain translational fidelity through strict charging by their cognate aminoacyl-tRNA synthetase and codon:anticodon base pairing with the mRNA at the ribosome. Mistranslation occurs when an amino acid not specified by the genetic code is incorporated into a protein. Since alanyl-tRNA synthetase uniquely recognizes a G3:U70 base pair in alanine tRNAs and the anticodon plays no role in charging, alanine tRNA variants with anticodon mutations have the potential to mistranslate alanine. Our goal was to quantify mis-incorporation of alanine into proteins in Saccharomyces cerevisiae strains expressing one of 57 different alanine tRNA anticodon variants. Using mass spectrometry, we observed mistranslation for 45 of the variants when expressed on single-copy plasmids.