Single channel planar lipid bilayer recordings of the melittin variant MelP5

• MelP5 forms bigger pores than melittin in planar lipid bilayers.
• MelP5 pores contain on average 10–12 peptides, melittin pores contain 3–8.
• MelP5 shows pore formation at 2 times lower concentrations than melittin.
• MelP5 occasionally forms stable, defined pores, unlike melittin.

MelP5 is a 26 amino acid peptide derived from melittin, the main active constituent of bee venom, with five amino acid replacements. The pore-forming activity of MelP5 in lipid membranes is attracting attention because MelP5 forms larger pores and induces dye leakage through liposome membranes at a lower concentration than melittin. Studies of MelP5 have so far focused on ensemble measurements of membrane leakage and impedance; here we extend this characterization with an electrophysiological comparison between MelP5 and melittin using planar lipid bilayer recordings. These experiments reveal that MelP5 pores in lipid membranes composed of 3:1 phosphatidylcholine:cholesterol consist of an average of 10 to 12 monomers compared to an average of 3 to 9 monomers for melittin. Both peptides form transient pores with dynamically varying conductance values similar to previous findings for melittin, but MelP5 occasionally also forms stable, well-defined pores with single channel conductance values that vary greatly and range from 50 to 3000 pS in an electrolyte solution containing 100 mM KCl.

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