SELF-ASSEMBLED ALPHA-HEMOLYSIN PORES IN AN S-LAYER-SUPPORTED LIPID BILAYER

The effects of a supporting proteinaceous surface-layer (S-layer) from Bacillus coagulans E38-66 on a 1,2-diphytanoyl-sn-glycero-3- phosphat idylcholine (DPhPC) bilayer were investigated. Comparative voltage cla mp studies on plain and S-layer supported DPhPC bilayers revealed no s ignificant difference in the capacitance. The conductance of the compo site membrane decreased slightly upon recrystallization of the S-layer . Thus, the attached S-layer lattice did not interpenetrate or rupture the DPhPC bilayer. The self-assembly of a pore-forming protein into t he S-layer supported lipid bilayer was examined, Staphylococcal alpha- hemolysin formed lytic pores when added to the lipid-exposed side. The assembly was slow compared to unsupported membranes, perhaps due to a n altered fluidity of the Lipid bilayer. No assembly could be detected upon adding alpha-hemolysin monomers to the S-layer-faced side of the composite membrane. Therefore. the intrinsic molecular sieving proper ties of the S-layer lattice do not allow passage of alpha-hemolysin mo nomers through the S-layer pores to the lipid bilayer. In comparison t o plain lipid bilayers, the S-layer supported lipid membrane had a dec reased tendency to rupture in the presence of alpha-hemolysin. (C) 199 8 Elsevier Science B.V.