Uses
Inhibits eukaryotic RNA-polymerase II with high efficiency, but not eukaryotic RNA-polymerase I, or bacterial or viral RNA-polymerases. Inhibits mammalian protein synthesis.
Biological Activity
α-amanitin, the most deleterious toxin of a. phalloides to humans, inhibits rna polymerase ii (rnapii), causing hepatic and renal failure.
Biochem/physiol Actions
The major toxic constituent of the mushroom, Amanita phalloides, inhibits eukaryotic RNA polymerase II and III, but does not inhibit RNA polymerase I or bacterial RNA polymerase. Inhibits mammalian protein synthesis.
Enzyme inhibitor
This bicyclic octapeptide toxin (FW = 918.98 g/mol; CAS 23109-05-9;
LD50 = 0.1 mg/kg i.p in albino mice) from the the death-cap fungus
Amanita phalloides binds very tightly to eukaryotic RNA polymerase II (Ki
≈ 10 nM) and less tightly to eukaryotic RNA polymerase III (Ki ≈ 1 μM),
blocking mRNA synthesis and inducing cytolysis of hepatocytes and
kidney cells. a-Amanitin istable at room temperature, soluble in water and
ethanol, and melts with decomposition at 254-255°C. Caution: Gloves
should be worn, and measures should be taken to avoid inhalation.
Symptoms of a toxic dose may not appear for 6-15 hours after exposure.
More than 90% of deaths caused by mushroom poisonings are due to A.
phalloides and related species. Target (s) : RNA polymerase II;
RNA polymerase III; yeast RNA polymerase B; RNA
polymerase I; certain plant RNA polymerases (e.g., plant RNA
polymerase II (); DNA-directed DNA polymerase; DNA-directed
RNA polymerase.
in vivo
The intravenous LD50 dose of alpha-Amanitin is 0.327 mg/kg body weight after intravenous injection into BALB/c mice. After 12 h of alpha-Amanitin injection in caudal vein, the levels of WBC, RBC and HGB decrease significantly, while those of BUN and Crea increase significantly in serum. alpha-Amanitin inhibits some genes (Hsp90b1, Irx4, etc.), whose encoded proteins regulate the RNA polymerase II activity. alpha-Amanitin down-regulates some proteins (Nmi, Trpc5, etc.) taking part in the transcription progress[1]. alpha-Amanitin has potent activity in DTC suppression. Mice injected with alpha-Amanitin (0.4 mg/kg, i.p.)-treated cells maintain their body weight, while those receiving a peritoneal injection of MKN45 cells show a constant decrease in body weight[2].
IC 50
Traditional Cytotoxic Agents
storage
-20°C, protect from light,unstable in solution, ready to use.
