Ribosomal Incorporation of Consecutive β‑Amino Acids

Due to their unique
characteristics, which are not shared by canonical
α-peptides, peptides that contain stretches of consecutive β-amino
acids are attractive scaffolds for novel peptide drugs and nanomaterials.
Although ribosomal incorporation of single or nonconsecutive β-amino
acids into peptides has previously been reported, the incorporation
of consecutive β-amino acids has not yet been accomplished.
This is primarily due to their incompatibility with the ribosomal
translation system. Here, we took advantage of engineered β-aminoacyl-tRNAs
bearing optimized T-stem and D-arm motifs for enhancing binding affinity
to EF-Tu and EF-P, respectively. Combined with a reconstituted E. coli translation system and optimized translation
factor concentrations, up to seven consecutive β-amino acids
could be incorporated into a model peptide. Furthermore, the synthesis
of macrocyclic β-peptides closed by a thioether bond between
two d-α-amino acids is also demonstrated. This represents
the first example of the ribosomal synthesis of peptides containing
stretches of consecutive β-amino acids.