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Kinetics of pore formation by an antimicrobial peptide, magainin 2, in phospholipid bilayers
K Matsuzaki1, O Murase, K Miyajima
1Faculty of Pharmaceutical Sciences, Kyoto University, Japan.
Abstract:
The kinetics of the pore formation by magainin 2, an antimicrobial peptide from Xenopus laevis, in lipid vesicles was investigated. The pore formation was estimated by the efflux of a fluorescent dye, calcein, from large unilamellar vesicles composed of egg yolk phosphatidylglycerol. The time courses of the dye release were well-described by a novel model in which the peptide molecules translocate from the outer to the inner monolayer by forming a pore. The concentration dependence of the leakage rate suggested that the pore consists of pentameric magainin. The obtained kinetic parameters estimate that, at a lipid-to-peptide molar ratio of 117, 9 pores with a lifetime of 40 microseconds open per second per vesicle in the initial phase. The apparent deactivation of the pore with increasing time can be ascribed to the reduced peptide density in the outer leaflet due to the translocation. Incorporation of phosphatidylcholine destabilized the pore, indicating the importance of anionic lipids in the stable pore formation.
Insights
Antimicrobial peptide magainin 2 forms pores in lipid vesicles. A novel model shows peptide translocation, with pore formation dependent on anionic lipids for stability.
Area of Science:
- Biophysics
- Biochemistry
- Membrane Biology
Background:
- Antimicrobial peptides (AMPs) are crucial for innate immunity.
- Magainin 2, an AMP from Xenopus laevis, exhibits membrane-disrupting properties.
- Understanding AMP-lipid interactions is key to antimicrobial drug development.
Purpose of the Study:
- To investigate the kinetics of pore formation by magainin 2 in lipid vesicles.
- To elucidate the mechanism of magainin 2-induced pore formation and its dependence on lipid composition.
Main Methods:
- Utilized large unilamellar vesicles (LUVs) composed of egg yolk phosphatidylglycerol.
- Monitored calcein dye efflux as a measure of pore formation.
- Developed and applied a novel kinetic model to describe dye release.
Main Results:
- Dye release kinetics were accurately described by a model involving peptide translocation and pore formation.
- Pore formation was concentration-dependent, suggesting a pentameric structure of magainin 2.
- Estimated pore formation rate and lifetime at a specific lipid-to-peptide ratio.
- Observed pore destabilization upon incorporation of phosphatidylcholine, highlighting the role of anionic lipids.
Conclusions:
- Magainin 2 forms pores via peptide translocation across lipid bilayers.
- Anionic lipids are essential for the stable formation of magainin 2 pores.
- The study provides kinetic insights into AMP-induced membrane disruption.