Figure 3.

Increasing the relative abundance of Tyr-specific tRNAs improves N-Me Tyr incorporation efficiency. (A) Schematic depicting the supplementation of translations with precharged, N-methylated Tyr-specific tRNA to increase the relative abundance of N-Me Tyr-tRNA. (B) MALDI-TOF mass spectrum showing products from a translation supplied with Tyr-precharged, N-methylated total tRNA only; (C−F) mass spectra showing products obtained when N-Me Tyr-tRNA was added to the indicated percentage of total tRNA. As the fraction of N-Me Tyr-tRNA in total tRNA was increased, the ratio of the intensity of the desired N-methyl peptide peak to that of the truncation product (MH₆M) peak (m_calcd = 1131.3) became larger, indicating more efficient incorporation of N-Me Tyr. The origin of the minor signal a (m_obs = 1591.4) is unknown, although it may represent a nonpeptide artifact.