Lipid‐Protein‐Interaction in Model Membranes: Binding of Melittin to Lecithin Bilayer Vesicles

Abstract

AbstractWe have studied the interaction of melittin with lecithin bilayer membranes. Fluorescence polarisation measurements were performed beside the use of excimer forming pyrene derivatives.1. Diphenyl hexatriene, a fluorescence polarisation probe, was used to investigate the lipid phase transition. Addition of melittin leads to an increase of the transition temperature. Characteristic breaks were obtained plotting Tu as a function of the melittin concentration. The change in the width of the phase transition gives an indication of phase separation phenomenon.2. Pure pyrene lecithin membranes were agitated by melittin. A dramatic decrease in the excimer to monomer ratio was observed showing the same characteristic breaks.3. No change in the lipid phase transition temperature was obtained using pyrene decanoic acid and pyrene lecithin as probe molecules. Pyrene lecithin is involved in the lipid‐protein‐complex and therefore prevented from undergoing the lipid phase transition. Rigid patches surrounding the peptide molecule were formed. The pyrene decanoic acid is squeezed out from these regions leading to an increase of the excimer yield in the bulk lipid.4. High melittin concentration (c > 10 mole‐%) leads to a membrane disruption followed by the formation of a stable melittin micell furnished with lipids.