Identification of brevinin-1EMa-derived stapled peptides as broad-spectrum virus entry blockers.

Based on the previously reported 13-residue antibacterial peptide analog, brevinin-1EMa (FLGWLFKVASKVL, peptide B), we attempted to design a novel class of antiviral peptides. For this goal, we synthesized three peptides with different stapling positions (B-2S, B-8S, and B-5S). The most active antiviral peptide with the specific stapling position (B-5S) was further modified in combination with either cysteine (B-5S3C, B-5S7C, and B-5S10C) or hydrophilic amino acid substitution (Bsub and Bsub-5S). Overall, B, B-5S, and Bsub-5S peptides showed superior antiviral activities against enveloped viruses such as retrovirus, lentivirus, hepatitis C virus, and herpes simplex virus with EC50 values of 1-5 µM. Murine norovirus, a non-enveloped virus, was not susceptible to the virucidal actions of these peptides, suggesting the virus membrane disruption as their main antiviral mechanisms of action. We believe that these three novel peptides could serve as promising candidates for further development of membrane-targeting antiviral drugs in the future.

Helix stabilization by stapled N-capping box.

The N-capping box is a distinct helix-stabilizing motif frequently found in proteins. In this study, we examined a ruthenium-mediated intramolecular backbone to side chain macrocyclization as a rigidified mimicry of the N-capping box. Experimental data indicate that the 15-membered macrocycle formed by a hept-4-enoyl staple, which directly tethers the α-amino group of N1 residue and the α-carbon of N3 residue, is highly effective in stabilizing helical structures of short peptides.