Exploring peptide membrane interaction using surface plasmon resonance: differentiation between pore formation versus...

Area of Science:

• Biochemistry
• Biophysics
• Membrane Biology

Background:

• Lytic peptides are crucial in biological defense and offense.
• Understanding their membrane interaction mechanisms is key to target cell selection.
• Previous techniques limited direct detection of peptide-membrane interaction steps.

Purpose of the Study:

• To utilize surface plasmon resonance (SPR) to study lytic peptide interactions with lipid bilayers.
• To differentiate between membrane binding and insertion steps for various lytic peptides.
• To elucidate the distinct mechanisms of pore formation versus carpet mechanisms.

Main Methods:

• Surface Plasmon Resonance (SPR) using L1 sensor chips for lipid bilayers.
• Hybrid monolayer (HPA) sensor chips for detailed analysis.
• Fitting SPR data to interaction models to quantify binding and insertion.

Main Results:

• Melittin exhibits significantly stronger binding to zwitterionic membranes (PC/cholesterol) via inner leaflet insertion.
• Magainin and melittin diastereomers show weaker binding to zwitterionic membranes and do not insert into the inner leaflet.
• All investigated peptides bind more strongly to negatively charged membranes (PE/PG) due to electrostatic attraction, employing a carpet mechanism.

Conclusions:

• SPR is a powerful tool for real-time monitoring of membrane-active peptide mechanisms.
• Melittin forms transmembrane pores in zwitterionic membranes, while magainin and its diastereomer act via a carpet mechanism.
• Peptide selectivity is governed by differential interactions with membrane leaflets, driven by charge and lipid composition.