Pores formed in lipid bilayers and in native membranes by nodularin, a cyanobacterial toxin

Nodularin (NODLN), a cyclic pentapeptide hepatotoxin from the cyanobacterium Nodularia spumigena, induces pores in bilayers of diphytanoyl lecithin (DPhL) and in locust muscle membrane. NODLN increases the surface pressure of a DPhL monolayer; except when the surface pressure of the monolayer is high when the toxin causes a reduction of this parameter. NODLN pores exhibit many open conductance states; the higher state probabilities increasing when the transmembrane pressure is increased. The results from these studies are discussed in terms of two models for a NODLN pore, a torroidal model and a barrel-stave model. The edge energy of the NODLN pore of 1.4 x 10(-12) J/m is determined.