[Interaction of cardiotoxin from the venom of the cobra Naja naja oxiana with phospholipid membrane model systems].

Surface activity of cardiotoxin from the venom of cobra Naia naja oxiana and an acetylated analog of the cardiotoxin was investigated on the water-air interface. The interaction of these substances with lipid monolayers and bimolecular membrane was also studied. It was shown that on the water-air interface cardiotoxin can form two different types of monolayers with different conformations of molecules. Cardiotoxin is found to form complexes with phospholipids due to interaction of positive charges of amino groups of lysin with phosphate groups of lipid molecules. One molecule of toxin is able to complex up to 10 molecules of lipid. The complex formed has a high surface activity, much more than that of the pure protein. Cardiotoxin increases the anion conductivity of bimolecular membranes. The nature of this phenomen is studied. A hypothetical mechanism of biological activity of caridotoxin is offered. It is supposed that not cardiotoxin as that, but its complex with phospholipid is the active agent.