Multiple membrane interactions and versatile vesicle deformations elicited by melittin.

Area of Science:

• Membrane biophysics
• Peptide-membrane interactions

Background:

• Melittin is a model peptide for studying membrane interactions.
• The precise mechanisms behind melittin's diverse membrane effects are not fully understood.

Purpose of the Study:

• To investigate the mechanisms of melittin-induced changes in giant liposomes.
• To correlate melittin's structural and binding states with observed membrane effects.

Main Methods:

• Direct real-time imaging of giant liposomes using dark-field optical microscopy.
• Analysis of melittin's secondary structure via circular dichroism.
• Assessing melittin-membrane binding using cosedimentation and fluorescence quenching.
• Visualizing structural changes with electron microscopy.

Main Results:

• Melittin induced three distinct effects: increasing membrane area, phased shrinkage, or solubilization, dependent on lipid charge and lipid-melittin ratio.
• Phased shrinkage involved liposome surface particle formation and rapid size reduction.
• Melittin adopted different secondary structures (α-helix, β-like, disordered) corresponding to each observed effect.
• Melittin exhibited distinct membrane-binding states and hydrophobic interactions based on the induced effect.

Conclusions:

• Melittin's varied effects on liposomes stem from its ability to adopt different structures.
• The binding state and conformational flexibility of melittin are crucial for its diverse membrane interactions.
• Understanding these structure-function relationships provides insight into peptide-lipid interactions.