Fig. 5: Proteome-wide mass spectrometry detecting stop codon readthrough (SCR) events in 16 peptides mapping to 15 proteins in E. coli.

A We detected SCR in 0.23% of TAA E. coli proteins and 0.77% of TGA E. coli proteins. While we found that TAA could be miscoded by numerous amino acids with similar frequencies, TGA was most often miscoded by Trp. B The occurrence of an additional stop codon in a 15, 30, and 60-nt window downstream of the stop codon correlated with the protein synthesis accuracy of the stop codon in the E. coli genome of the K12 MG1655 strain. TGA, as the least accurate stop codon, had the highest frequency of an additional stop codon in the 3’ regions of genes. C We detected more cases of SCR in E. coli samples grown at l8 °C than at 37 °C. Five genes were exclusively detected at 18 °C, and only two genes were exclusively detected at 37 °C. D The identity of the nucleotide downstream of the stop codon modulated the SCR probability. While G decreased the protein synthesis termination accuracy, T increased it. Source data are provided as a Source data file.