Impact of the antimicrobial peptide Novicidin on membrane structure and integrity.
We have studied the impact of an 18-residue cationic antimicrobial peptide Novicidin (Nc) on the structure and integrity of partially anionic lipid membranes using oriented circular dichroism (OCD), quartz crystal microbalance with dissipation (QCM-D), dual polarization interferometry (DPI), calcein dye leakage and fluorescence spectroscopy. OCD consistently showed that Nc is bound in an α-helical, surface bound state over a range of peptide to lipid (P/L) ratios up to ~1:15. Realignment of Nc at higher P/L ratios correlates to loss of membrane integrity as shown by Laurdan fluorescence spectroscopy and by loss of lipid alignment in DPI analysis. Laurdan generalized polarity shows a decrease in water accessibility or mobility in the hydrophobic/hydrophilic interface of the lipid membrane, consistent with rearrangement of lipid packing. QCM-D studies on the interaction of Nc with lipid membranes emphasize the importance of including the dissipation factor in data analysis, revealing formation of a highly hydrated film after exposure to ≥3 μM Nc. Our findings suggest a carpet mechanism of membrane disruption in which peptide binding first induces leakage at a critical surface concentration, probably through formation of transient pores or transient disruption of the membrane integrity, followed by more extensive membrane disintegration at higher P/L ratios.
Nielsen
Søren B
SB
Interdisciplinary Nanoscience Center (iNANO), Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10C, DK - 8000 Aarhus C, Denmark.
Otzen
Daniel E
DE
D000890:Anti-Infective Agents / Q000737:chemistry*; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry*; D017433:Protein Structure, Secondary
D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D008051:Lipid Bilayers; C554278:novicidin