 Amatoxins consist of at least eight compounds with a similar structure , that of eight amino @-@ acid rings ; they were isolated in 1941 by Heinrich O. Wieland and Rudolf <unk> of the University of Munich . Of the amatoxins , α @-@ amanitin is the chief component and along with β @-@ amanitin is likely responsible for the toxic effects . Their major toxic mechanism is the inhibition of RNA polymerase II , a vital enzyme in the synthesis of messenger RNA ( mRNA ) , microRNA , and small nuclear RNA ( snRNA ) . Without mRNA , essential protein synthesis and hence cell metabolism grind to a halt and the cell dies . The liver is the principal organ affected , as it is the organ which is first encountered after absorption in the gastrointestinal tract , though other organs , especially the kidneys , are susceptible . The RNA polymerase of Amanita phalloides is insensitive to the effects of amatoxins , so the mushroom does not poison itself . 
