Major toxin that belongs to the bicyclic heptapeptides called phallotoxins (PubMed:24613547). Although structurally related to amatoxins, phallotoxins have a different mode of action, which is the stabilization of F-actin (PubMed:24613547). Phallotoxins are poisonous when administered parenterally, but not orally because of poor absorption (PubMed:24613547). Processed by the macrocyclase-peptidase enzyme POPB to yield a toxic cyclic heptapeptide (By similarity). POPB first removes 10 residues from the N-terminus (By similarity). Conformational trapping of the remaining peptide forces the enzyme to release this intermediate rather than proceed to macrocyclization (By similarity). The enzyme rebinds the remaining peptide in a different conformation and catalyzes macrocyclization of the N-terminal 7 residues (By similarity). Belongs to the MSDIN fungal toxin family.