Membrane insertion and bilayer perturbation by antimicrobial peptide CM15

Area of Science:

• Biochemistry
• Molecular Biology
• Membrane Biophysics

Background:

• Antimicrobial peptides (AMPs) are crucial for innate immunity and are explored as novel antibiotics.
• Understanding AMP-membrane interactions is key to their mechanism of action, but details remain elusive.
• CM15, a synthetic AMP, forms pores and exhibits bactericidal activity.

Purpose of the Study:

• To investigate the molecular mechanism of membrane disruption by the synthetic antimicrobial peptide CM15.
• To determine how CM15 concentration affects its insertion into lipid bilayers.
• To assess the impact of CM15 accumulation on membrane lipid properties and permeability.

Main Methods:

• Site-directed spin labeling electron paramagnetic resonance (SDSL-EPR) was used to study CM15 analogs.
• Phospholipid-analog spin labels were employed to monitor changes in lipid dynamics.
• The effect of increasing CM15 concentration on peptide insertion and membrane properties was analyzed.

Main Results:

• Increasing CM15 concentration led to deeper immersion of its N-terminal domain into the lipid bilayer.
• Minimal changes in lipid rotational dynamics were observed, primarily at the membrane surface.
• CM15 accumulation significantly increased membrane permeability to polar solutes.

Conclusions:

• CM15 insertion depth increases with concentration, influencing membrane properties.
• CM15-induced membrane permeability to polar solutes is a key aspect of its mechanism.
• These findings provide insights into the molecular basis of CM15's antimicrobial activity.