Effects of the cationic antimicrobial peptide eumenitin from the venom of solitary wasp Eumenes rubronotatus in planar lipid bilayers: surface charge and pore formation activity.

Eumenitin, a novel cationic antimicrobial peptide from the venom of solitary wasp Eumenes rubronotatus, was characterized by its effects on black lipid membranes of negatively charged (azolectin) and zwitterionic (1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) or DPhPC-cholesterol) phospholipids: surface potential changes, single-channel activity, ion selectivity, and pore size were studied. We found that eumenitin binds preferentially to charged lipid membranes as compared with zwitterionic ones. Eumenitin is able to form pores in azolectin (G1=118.00+/-3.67pS or G2=160.00+/-7.07pS) and DPhPC membranes (G=61.13+/-7.57pS). Moreover, cholesterol addition to zwitterionic DPhPC membranes inhibits pore formation activity but does not interfere with the binding of peptide. Open pores presented higher cation (K+) over anion (Cl-) selectivity. The pore diameter was estimated at between 8.5and 9.8 angstroms in azolectin membranes and about 4.3 angstroms in DPhPC membranes. The results are discussed based on the toroidal pore model for membrane pore-forming activity and ion selectivity.