Penetration of phospholipid monolayers by cardiotoxins

Abstract

The monomolecular film technique was used to compare the specific interactions of 4 cardiotoxins from Naja mossambica mossambica with different phospholipids. The interaction of cardiotoxins (10-7 M) with neutral and negatively charged phospholipids up to high surface pressures (45 dyn/cm) was demonstrated. In the presence of a phospholipid monolayer, the surface activity of cardiotoxins became greater than that observed at the air-water interface. Neurotoxins of the same venom did not penetrate a phospholipid film, even at low surface pressure (15 dyn/cm). The apparent molecular area of cardiotoxin 3 during its insertion into a negatively charged phospholipid film was quantitatively defined. As a function of surface pressure of the membrane .apprx. 25 dyn/cm, cardiotoxins may exist in 2 different configurations, flat (1400 .ANG.2) or edgewise (420 .ANG.2). This result could account for the lytic activity of this type of toxin.