Relevance of amphiphilicity and helicity on the antibacterial action of a histatin 5-derived peptide

Peptide dhvar4, derived from the active domain of our salivary peptide histatin 5, bears a Phe residue in the middle of its hydrophilic face when folded into an alpha-helix. We then synthesized an analog with this Phe replaced by Lys and two analogs preserving Phe but bearing two and three alpha-aminoisobutyric acid (Aib) residues to stabilize the helical structure. The aim of this design was to verify which of the two features is more favorable to the biological activity. We performed a conformational study by means of circular dichroism and nuclear magnetic resonance, made antibacterial tests, and assessed the stability of the peptides in human serum. We observed that amphiphilicity is more important than helix stability, provided a peptide can adopt a helical conformation in a membrane-mimetic environment. Peptide dhvar4 bears a Phe residue in the middle of its hydrophilic face when folded into an alpha-helix. A dhvar4 analog with this Phe replaced by Lys and two analogs preserving Phe but bearing two and three alpha-aminoisobutyric acid (Aib) residues were synthesized to verify which of the two features is more favorable to the biological activity. image