Effects of five-membered ring amino acid incorporation into peptides for coiled coil formation

A five-membered ring amino acid (Ac₅c), the peptides of which exhibit a preference for helical secondary structures, was introduced into peptides for the purpose of designing coiled coil peptides with high binding affinities. We prepared five types of peptides containing Ac₅c with different numbers or at different positions. The incorporation of Ac₅c into peptides enhanced their α-helicities; however, in contrast to our expectations, it did not result in stable coiled coil formation. The structures of side chains in hydrophobic amino acids, not α-helicities appeared to be important for stable hydrophobic interactions between peptides. Although we were unable to develop coiled coil peptides with high binding affinities, the present results will be useful for designing novel coiled coil peptides.