Figure 3.

Mechanism of action of Cyt proteins. (a) Pore-forming model; once Cyt toxins interact with phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin, they undergo a conformational change that helps recruit six Cyt monomers and assemble them into an open-umbrella structure, which results in a pore-formation and subsequent membrane permeabilization and larva death. (b) Detergent effect model; high Cyt toxin concentration binds to the lipid bilayer on cell membrane surface and destroys it through a detergent-effect. Both, the pore-formation model and detergent model are not mutually exclusive, because, the detergent effect acts at high Cyt toxins concentrations, while the pore-forming model acts at low Cyt toxins concentrations. A, Solubilization. B, Activation by proteolysis. C, Recognition of membrane receptor. Created with Biorender.com.