Mechanism of action of Bacillus thuringiensis var israelensis insecticidal δ‐endotoxin

Abstract

Bacillus thuringiensis var israelensisδ‐endotoxin protein active against mosquitoes was inactivated by prior incubation with lipids extracted from Aedes albopictus cells. Experiments with lipid dispersions and multilamellar liposomes showed that the toxin binds to phosphatidyl choline, sphingomyelin and phosphatidyl ethanolamine provided these lipids contain unsaturated fatty acids. Phosphatidyl serine binds toxin less efficiently and phosphatidyl inositol, cardiolipin, cerebroside and cholesterol show no affinity for the toxin. The results suggest an insecticidal mechanism in which interaction of toxin with specific plasma membrane lipids causes a detergent‐like rearrangement of the lipids, leading to disruption of membrane integrity and eventual cytolysis.