Phalloidin is a natural mycotoxin first isolated from the death cap mushroom, A. phalloides. It binds F-actin and stabilizes actin fibers. Fluorescently labeled phalloidin is commonly used to stain F-actin in cells.
Phalloidin has been used:
- As a supplement in PEM buffer and dimethyl sulfoxide (DMSO).
- As a drug.
- In immunohistochemistry to stain F-actin.
ChEBI: A homodetic bicyclic heptapeptide having a sulfide bridge.
Phalloidin is a phallotoxin produced by death cap mushroom Amanita phalloides. It is a cyclic peptide, which interacts with actin, and this was first identified in phalloidin-poisoned rats. It is a heptapeptide, cyclic in nature, with a crosslink between tryptophan at position 6 and cysteine at position 3. The side chain of amino acid 7 (γ-δ-dihydroxyleucine) in phalloidin, is accessible to modifications, through which fluorescently labeled phalloidin compounds can be produced.
Toxin that binds polymeric F actin, stabilizing it and interfering with the function of actin-rich structures.
Poison by ingestion, intraperitoneal, and intravenous routes. Mutation data reported. Whenheated to decomposition it emits toxic fumes of SOx, and NOx.
This bicyclic heptapeptide toxin (FW = 788.88 g/mol; CAS 17466-45-4) is was first isolated from the poisonous green fungus Amanita phalloides. Primary Mode of Action: Phalloidin binds preferentially to filamentous actin; little or no binding to globular actin has been detected. such preferential action stimulates actin polymerization, and phalloidin lowers the actin monomer critical concentration by 30x, from 50-100 nM down to 2-3 nM. When present at 1 to 10 concentration ratio of phalloidin to total actin subunits, actin filaments are also greatly stabilized toward depolymerization. Effects on Actin Filaments: Cellular processes requiring filament disassembly are likewise inhibited. Depolymerization of F-actin by cytochalasins, potassium iodide, and elevated temperatures are inhibited by phalloidin binding. Because the toxin and its fluorescent derivatives are relatively small, a wide variety of actin-binding proteins can still bind to phalloidin-labeled filamentts. Perhaps more significantly, phalloidin-labeled actin filaments retain many of their functional properties, such that phalloidin-labeled, glycerinated muscle fibers can still contract, and labeled actin filaments still move on myosin that has been tethered to solid-phase substrates. Phalloidin can be also be used to assess the relativeconcentrations of these two forms of actin as well as a means to label actin filaments in a cell (See Phallacidin).
