ADCs Toxins, Phalloidin is a bicyclic heptapeptide toxin of the death cap mushroom toxin family aslo called phallotoxins. Phalloidin binds F-actin, preventing its depolymerization and is poisoning the cell. It specially binds at the inferface between F-acting subunits, locking adjacetn subunits togeter. Phalloidin binds specifically to polymeric and oligomeric forms of actin and not to monomeric actin.