In Vitro Selection of Foldamer-Like Macrocyclic Peptides Containing 2‑Aminobenzoic Acid and 3‑Aminothiophene-2-Carboxylic Acid

Aromatic
cyclic β2,3-amino acids (cβAAs),
such as 2-aminobenzoic acid and 3-aminothiophene-2-carboxylic acid,
are building blocks that can induce unique folding propensities of
peptides. Although their ribosomal elongation had been a formidable
task due to the low nucleophilicity of their amino groups, we have
recently overcome this issue by means of an engineered tRNAPro1E2 that enhances their incorporation efficiency into nascent peptide
chains. Here we report ribosomal synthesis of a random macrocyclic
peptide library containing aromatic and aliphatic cβAAs, and
its application to de novo discovery of binders against human IFNGR1
and FXIIa as model targets. The potent binding peptides showed not
only high inhibitory activity but also high protease resistance in
human serum. Moreover, these cβAAs play a critical role in exhibiting
their properties, establishing a discovery platform for de novo foldamer-like
macrocycles containing such unique building blocks.