Figure 7.

Model of action of Mt-II. The toxin interacts with a yet unidentified receptor (R), embedded in a membrane microdomain. R activates ATP channels by inducing the release of calcium from intracellular stores and/or by other mechanisms. The released ATP stimulates purinergic receptors within the same plasma membrane microdomain inducing a further release of ATP. The extracellular ATP activates a signaling cascade leading to changes in the composition of the plasma membrane, which in turn promotes the insertion of Mt-II into the lipid bilayer with consequent osmotic cell lysis. It is proposed that this hypothesis may be valid also for other membrane-active toxins and peptides