Magainin 2-Induced Pore Formation in the Lipid Membranes Depends on Its Concentration in the Membrane Interface

Abstract

Antimicrobial peptide magainin 2 forms pores in lipid membranes to induce leakage of internal contents of cells, which is a main cause of its bactericidal activity. However, the conditions and the mechanism of its pore formation remain unclear. In this report, to reveal the effect of the surface charge density of membranes on magainin 2-induced pore formation, we investigated the interaction of magainin 2 with giant unilamellar vesicles (GUVs) composed of a mixture of electrically neutral dioleoylphosphatidylcholine (DOPC) and negatively charged dioleoylphosphatidylglycerol (DOPG) in various ratios, using the single GUV method. We found that magainin 2 induced pores in the membranes of all kinds of single GUVs. For GUVs with the same charge density, the rate of the pore formation increased with magainin 2 concentration. The magainin 2 concentrations in a buffer required to induce the same rate of the pore formation greatly increased with a decrease in the surface charge density; e.g., the magainin 2 concentrations required for the pore formation in 30% DOPG/70% DOPC-GUVs were 50 times higher than those in 60% DOPG/40% DOPC-GUVs. However, after we converted the magainin 2 concentration in the buffer into that in the membrane interface, Xbmag, we found that Xbmag mainly determines the rate of the pore formation in various GUVs. These data support our model of two-state transition from the binding state to the pore state of the GUV for magainin 2-induced pore formation.

Common mechanism unites membrane poration by amyloid and antimicrobial peptides

“…rIAPP and magainin 2 maintain stable pores at equilibrium. Peptides were first equilibrated with 200 μM 1,2-dioleoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (DOPG) liposomes (in monomer units) for 48 h. Anionic DOPG was chosen as a simple model that reflects the importance of electrostatic interactions for binding and activity by both peptides (23,24). Leakage kinetics was then assessed by adding DPX extraluminally.…”

Optical Microscopy of Giant Vesicles as a Tool to Reveal the Mechanism of Action of Antimicrobial Peptides and the Specific Case of Gomesin

“…In fact, when comparing results obtained from GUVs and LUVs, special caution should be given to the different conditions assessed in both experiments, as for instance, the significantly lower lipid concentration in GUVs experiments. Later, the same authors showed that the percentage of leakage was directly associated with the amount of membrane-bound magainin 2, modulated by the molar fraction of the anionic lipid PG in the membrane [46]. The kinetic pathway of magainin 2-induced pore formation was investigated in a subsequent work [47] through encapsulation of dyes of different size (1.4-3.6 nm radii).…”

Single-Vesicle Detection and Analysis of Peptide-Induced Membrane Permeabilization

“…In To complete the present discussion, it should be mentioned that giant unilamellar lipid vesicles (GUVs) with a diameter of ∼3 µm or more have been employed instead of LUVs to study the activity of membrane-active peptides. 41,49 The advantage of using GUVs is that they are sufficiently large that fluxes of fluorescent molecules into or out of individual vesicles can be directly imaged, including fluxes of fluorescent molecules of different sizes. 50 …”