Leucyl/phenylalanyl(L/F)‐tRNA‐protein transferase‐mediated aminoacyl transfer of a nonnatural amino acid to the N‐terminus of peptides and proteins and subsequent functionalization by bioorthogonal reactions

We report here a new strategy for derivatizing peptides and proteins at the N‐terminus. To achieve this, a nonnatural amino acid was charged onto a tRNA and then enzymatically transferred to a lysine (Lys) unit at the N‐terminus of a peptide or a protein by using L/F‐tRNA‐protein transferase. By using the chemoenzymatic technique, β‐(2‐quinolyl)‐ L ‐alanine, p‐azido‐ L ‐phenylalanine, and p‐acetyl‐ L ‐phenylalanine were introduced to the N‐terminus. The latter two nonnatural amino acids possess bioorthogonal functional groups to which artificial tags can be introduced. Actually, a biotin tag was coupled to the bioorthogonal ketone group of acetylphenylalanine at the N‐terminus of a peptide. N‐terminal‐specific biotinylation and fluorescence derivatization of the bioorthogonal azido‐containing protein or peptide was also carried out based on a [3 + 2] cycloaddition. The enzymatic transfer of a nonnatural amino acid to the N‐terminus of target peptides or proteins was also successfully achieved in the presence of other peptides or crude protein mixtures. © 2007 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 88: 263–271, 2007. This article was originally published online as an accepted preprint. The ‘Published Online’ date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com