Binding and reorientation of melittin in a POPC bilayer: Computer simulations
We performed, using an all-atom force field, molecular dynamics computer simulations to study the binding of melittin to the POPC bilayer and its subsequent reorientation in this bilayer. The binding process involves a simultaneous folding and adsorption of the peptide to the bilayer, followed by the creation of a “U shaped” conformation. The reorientation of melittin from the parallel to the perpendicular conformation requires charged residues to cross the hydrophobic core of the bilayer. This is accomplished by a creation of defects in the bilayer that are filled out with water. The defects are caused by peptide charged residues dragging the lipid headgroup atoms along with them, as they reorient. With increased concentration of melittin water defects form stable pores; this makes it easier for the peptide N-terminus to reorient. Our results complement experimental and computational observations of the melittin/lipid bilayer interaction. âº Melittin can adopt a shallow “U-shaped” conformation upon binding to a POPC bilayer. âº Reorientation of melittin at a P/L ratio = 1/128 causes water defects in the bilayer. âº At P/L = 4/128, upon reorientation, the water defects form stable toroidal pores. âº Pseudo-transmembrane conformation is an intermediate in the reorientation process.