PORES FORMED IN LIPID BILAYERS AND IN NATIVE MEMBRANES BY NODULARIN, A CYANOBACTERIAL TOXIN

Nodularin (NODLN), a cyclic pentapeptide hepatotoxin from the cyanobac terium Nodularia spumigena, induces pores in bilayers of diphytanoyl l ecithin (DPhL) and in locust muscle membrane. NODLN increases the surf ace pressure of a DPhL monolayer; except when the surface pressure of the monolayer is high when the toxin causes a reduction of this parame ter. NODLN pores exhibit many open conductance states; the higher stat e probabilities increasing when the transmembrane pressure is increase d. 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 edg e energy of the NODLN pore of 1.4 x 10(-12) J/m is determined.