J.-H. Lin and A. Baumgärtner

We have investigated the interaction of proteins with hydrated lipid bilayer membranes using molecular dynamics simulations. Two problems have been addressed : the protein-insertion problem and the stability of a protein pore embedded in a bilayer membrane. It is shown that in contrast to previous studies single proteins do not insert spontaneously, but are probibited to do so by the interfacial barrier of the water-lipid interface. A tight protein pore expands due to electrostatic repulsion among the a-helices. The energetically unfavorable expansion-induced formation of an interface between the pore-lining acyl chains of the lipids and the pore water is transformed into an energetically more favorable toroidal pore structure where some lipid heads are translocated from the rim to the central part of the interface. It is hypothesized that pore growth, and hence cell lysis, is induced by a protein-mediated line tension of the pore.