Antimicrobial peptide magainin 2-induced rupture of single giant unilamellar vesicles comprising E. coli polar lipids.

Most antimicrobial peptides (AMPs) damage the cell membrane of bacterial cells and induce rapid leakage of the internal cell contents, which is a main cause of their bactericidal activity. One of the AMPs, magainin 2 (Mag), forms nanopores in giant unilamellar vesicles (GUVs) comprising phosphatidylcholine (PC) and phosphatidylglycerol (PG), inducing leakage of fluorescent probes. In this study, to elucidate the Mag-induced pore formation in lipid bilayer region in E. coli cell membrane, we examined the interaction of Mag with single GUVs comprising E. coli polar lipids (E. coli -lipid-GUVs). First, we investigated the Mag-induced leakage of a fluorescent probe AF488 from single E. coli -lipid-GUVs, and found that Mag caused rupture of GUVs, inducing rapid AF488 leakage. The rate constant of Mag-induced GUV rupture increased with the Mag concentration. Using fluorescence microscopy with a time resolution of 5 ms, we revealed the GUV rupture process: first, a small micropore was observed in the GUV membrane, then the pore radius increased within 50 ms without changing the GUV diameter, the thickness of the membrane at the pore rim concomitantly increased, and eventually membrane aggregates were formed. Mag bound to only the outer monolayer of the GUV before GUV rupture, which increased the area of the GUV bilayer. We also examined the physical properties of E. coli -lipid-GUVs themselves. We found that the rate constant of the constant tension-induced rupture of E. coli -lipid-GUVs was higher than that of PG/PC-GUVs. Based on these results, we discussed the Mag-induced rupture of E. coli -lipid-GUVs and its mechanism. [Display omitted] • Magainin 2 (Mag) induced rupture of E. coli -lipid GUVs, inducing rapid leakage. • Rate constant of Mag-induced rupture of GUVs (k r) increased with Mag concentration. • First a small micropore was formed, and grew rapidly with time to rupture the GUV. • Binding of Mag to the outer monolayer increased the area of the GUV bilayer. • Mechanical property of E. coli -lipid GUVs related to pore formation was elucidated. [ABSTRACT FROM AUTHOR]