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Modification of the N-terminus of membrane fusion-active peptides blocks the fusion activity
M Murata1, S Kagiwada, R Hishida
1Department of Biophysics, Faculty of Science, Kyoto University, Japan.
Abstract:
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.
Insights
Anionic peptides E5 and E5L mimic viral hemagglutinin fusion activity at acidic pH. N-terminal modifications significantly reduced this membrane fusion capability, highlighting the N-terminus's crucial role.
Area of Science:
- Biochemistry
- Molecular Biology
- Membrane Biophysics
Background:
- Influenza hemagglutinin (HA) mediates viral entry through membrane fusion.
- Amphiphilic anionic peptides can potentially mimic viral fusion proteins.
- Understanding peptide-membrane interactions is key to designing fusion mediators.
Purpose of the Study:
- To investigate the fusogenic activity of peptides E5 and E5L.
- To determine the role of N-terminal and C-terminal modifications on peptide-induced membrane fusion.
- To elucidate the mechanism underlying peptide-mediated membrane fusion.
Main Methods:
- Fusion assays using small and large unilamellar vesicles (SUVs/LUVs) composed of egg yolk phosphatidylcholine.
- Chemical modification of peptide N-termini (acetylation, acetimidylation) and C-termini (amidation).
- Lipid-membrane binding assays and Circular Dichroism (CD) spectroscopy to assess peptide structure and membrane interaction.
Main Results:
- Peptides E5 and E5L exhibited pH-dependent fusion activity, mimicking viral HA.
- N-terminal acetylation or acetimidylation drastically reduced fusion activity.
- C-terminal amidation did not significantly alter fusion activity.
- Modified peptides showed largely unchanged membrane binding, and maintained alpha-helical structures.
Conclusions:
- The N-terminus of peptides E5 and E5L is critical for their membrane fusion activity.
- While membrane binding and helical structure are maintained, N-terminal modifications abolish fusogenicity.
- The precise mechanism by which N-terminal modifications impact fusion remains to be elucidated.