Phalloidin belongs to a class of toxins called phallotoxins, which are found in the death cap mushroom (Amanita phalloides).

The major symptom of phalloidin poisoning is acute hunger due to the destruction of liver cells.

It was isolated from the death cap mushroom and crystallized by Feodor Lynen and Ulrich Wieland[1] in 1937.

They determined the presence of the sulfur atom using UV spectroscopy and found that this ring structure had a slightly shifted wavelength.

Once linearized, the amino acid sequence of de-sulfurized phalloidin was elucidated through Edman degradation by Wieland and Schön in 1955.

[5] The first post-translational modification of the 34-mer is proteolytic cleavage via a prolyl oligopeptidase (POP) to remove the 10-amino acid "leader" peptide.

Below is the general synthetic mechanism carried out by Anderson et al. in 2005 for the solid phase synthesis of ala7-phalloidin, which differs at residue 7 from phalloidin as indicated below.

[6] THPP stands for tetrahydropyranyl polystyrene linker, which is used to connect the molecule with the solid support during synthesis.

Note that the synthesis below is simply a general scheme to show the order of bond formation to connect the starting materials.

When introduced into the cytoplasm at low concentrations, phalloidin recruits the less polymerized forms of cytoplasmic actin as well as filamin into stable "islands" of aggregated actin polymers, yet it does not interfere with stress fibers, i.e. thick bundles of microfilaments.

[7] A high-resolution technique was developed to detect F-actin at the light and electron microscopic levels by using phalloidin conjugated to the fluorophore eosin which acts as the fluorescent tag.

[7] Consequently, immunofluorescence microscopy along with microinjection of phalloidin can be used to evaluate the direct and indirect functions of cytoplasmic actin in its different stages of polymer formation.