pellet holding a few hundred millionths of a gram of ricin to kill the Bulgarian broadcaster, Georgi Markov, who died 4 days after being attacked. Compared to amatoxins The toxins present in poisonous mushrooms such as Amanita phalloides are quite different from toxalbumins and are mostly secondary metabolites or amatoxins which do not readily break down under applied heat. They are potent inhibitors of RNA polymerase II, an enzyme vital in the synthesis of messenger RNA (mRNA), microRNA, and small nuclear RNA (snRNA). Without mRNA, the template for protein synthesis, cell metabolism stops. In this respect, their metabolic effect is similar to that of toxalbumins. External links 'Plant toxins and acute medicinal plant poisoning in children: A systematic literature review' See also References Plant proteins Plant toxins Poisons