Modification of the N-terminus of membrane fusion-active peptides blocks the fusion activity

The amphiphilic anionic peptides E5 and E5L can mimic the fusogenic activity of influenza hemagglutinin(HA). These peptides induced fusion of egg yolk phosphatidylcholine small or large unilamellar vesicles only at acidic pH in a similar manner to viral HA. Acetylation or acetimidylation of the N-terminus of the peptides drastically reduced the fusion activity of the intact peptides, while C-terminal amidation left the activity unchanged. The binding assay suggested that the interaction of the modified peptides with lipid membranes was almost unchanged in comparison with those of the parent peptides, and the CD spectra showed that these peptides were alpha-helical. The results showed the importance of the N-terminus of the peptides on the membrane fusion activity, although why the N-terminal modifications affect the activity is still unclear.