An antimicrobial peptide, magainin 2, induced rapid flip-flop of phospholipids coupled with pore formation and peptide translocation
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K Matsuzaki1, O Murase, N Fujii
1Faculty of Pharmaceutical Sciences, Kyoto University, Japan. katsumim@pharmsun.pharm.kyoto-u.ac.jp
Abstract:
The effect of an antimicrobial peptide, magainin 2, on the flip-flop rates of phospholipids was investigated by use of fluorescent lipids, i.e., anionic N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)dipalmitoyl-L-alpha- phosphatidylethanolamine (NBD-PE), 1-oleoyl-2-[12-((7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)- dodecanoyl]-L-alpha-phosphatidic acid (C12-NBD-PA), 1-oleoyl-2-[12- ((7-nitrobenz-2-oxa-1,3-diazol-4-yl)- amino)dodecanoyl]-L-alpha-phosphatidyl-L-serine (C12-NBD-PS), and zwitterionic 1-palmitoyl-2-[6-((7- nitrobenz-2-oxa-1,3-diazol-4-yl)amino)caproyl]-L-alpha-phosphatidy lcholine (C6-NBD-PC). Their intrinsic flip-flop half-lives at 30 degrees C in the absence of the peptide were 1.1 h, ca. 7 h, ca. 8 days, and > 2 days, respectively. The peptide accelerated the flip-flop half-lives of the fluorescent lipids to an order of minutes. Furthermore, the flip-flop was coupled with the membrane permeabilization and the peptide translocation [Matsuzaki, K., Murase, O., Fujii, N., & Miyajima, K. (1995) Biochemistry 34, 6521-6526], suggesting pore-mediated flip-flop. The flip-flop rate was independent of the initial labeling conditions (outer leaflet label or inner leaflet label). From these results, a model was proposed, in which the lipids translocate across the membrane by lateral diffusion along the wall of the pores composed of the peptides and the lipids. A simple theoretical calculation could explain the coupling of the flip-flop with the permeabilization.
Insights
The antimicrobial peptide magainin 2 dramatically accelerates phospholipid flip-flop across membranes, reducing half-lives to minutes. This process is linked to membrane permeabilization and peptide translocation, suggesting a pore-mediated mechanism for lipid transport.
Area of Science:
- Biochemistry
- Membrane Biophysics
- Antimicrobial Peptides
Background:
- Phospholipid flip-flop is crucial for membrane asymmetry and function.
- Antimicrobial peptides (AMPs) can interact with and permeabilize lipid bilayers.
- Understanding AMP-induced lipid dynamics is key to elucidating their mechanism of action.
Purpose of the Study:
- To investigate the effect of the antimicrobial peptide magainin 2 on phospholipid flip-flop rates.
- To explore the mechanism by which magainin 2 influences lipid transbilayer movement.
- To correlate flip-flop rates with membrane permeabilization and peptide translocation.
Main Methods:
- Utilized fluorescently labeled phospholipids (NBD-PE, C12-NBD-PA, C12-NBD-PS, C6-NBD-PC) to monitor flip-flop rates.
- Measured intrinsic flip-flop half-lives of lipids at 30°C in the absence of peptide.
- Assessed the impact of magainin 2 on flip-flop rates and coupled phenomena like membrane permeabilization.
Main Results:
- Magainin 2 significantly accelerated phospholipid flip-flop, reducing half-lives from hours/days to minutes.
- The accelerated flip-flop was coupled with membrane permeabilization and peptide translocation.
- Flip-flop rate was independent of the initial labeling position (outer or inner leaflet).
Conclusions:
- Magainin 2 induces a pore-mediated flip-flop mechanism for phospholipids.
- A proposed model suggests lipids translocate via lateral diffusion along peptide-lipid pores.
- This mechanism explains the observed coupling between flip-flop and membrane permeabilization.