Phalloidin

Phalloidin is a bicyclic heptapeptide toxin found in the deadly Amanita phalloides mushroom, also known as the death cap. It is one of the toxins responsible for the potentially fatal hepatotoxicity seen in Amanita phalloides poisoning.

Structure and Properties

Phalloidin is a cyclic peptide, composed of seven amino acids. Its structure is characterized by a tryptophan-dimer, which is responsible for its strong affinity to actin. Phalloidin is not a protein, but a smaller peptide. It is highly resistant to heat and enzymatic degradation due to its cyclic structure.

Mechanism of Action

Phalloidin binds to actin filaments in eukaryotic cells, stabilizing them and preventing their disassembly. This disrupts the normal dynamic turnover of actin, leading to cell death. The toxin's strong affinity for actin and its ability to disrupt actin dynamics make it a useful tool in the study of actin biochemistry.

Toxicity

Phalloidin is highly toxic if ingested, with symptoms of poisoning including severe abdominal pain, vomiting, and potentially fatal liver damage. However, it is not absorbed well from the gastrointestinal tract, and is therefore less toxic when ingested than when administered parenterally. The lethal dose in humans is not known with certainty.

Use in Research

Phalloidin is used in biological research to visualize and stabilize actin filaments in cells. It is often conjugated to a fluorescent dye, allowing it to be seen under a fluorescence microscope. This has made it a valuable tool in the study of the cytoskeleton and cell motility.

See Also

• Amanita phalloides
• Actin
• Cytoskeleton
• Cell motility

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  Phalloidin synthetic scheme

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  Phalloidin bound to F-Actin

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  Fluorescent cells stained with phalloidin

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  Phalloidin staining of actin filaments