|
|Section2= |Section3= }} ''alpha''-Amanitin or α-amanitin is a cyclic peptide of eight amino acids. It is possibly the most deadly of all the amatoxins, toxins found in several species of the ''Amanita'' genus of mushrooms, one being the death cap (''Amanita phalloides'') as well as the destroying angel, a complex of similar species, principally ''A. virosa'' and ''A. bisporigera''. It is also found in the mushrooms ''Galerina marginata'' and ''Conocybe filaris''. The oral of amanitin is approximately 0.1 mg/kg for rats. The structure of the polypeptide is atypical of most polypeptides, due to the branching of the amino acid chain. A cross bridge between 6-hydroxy-tryptophan and cysteine allows the formation of a second "inner loop," as seen in the diagram at right. The "outer loop" is formed by the normal peptide bond of the carboxyl terminus to the amino terminus of the peptide chain. Unlike most cyclic peptides, amatoxins (and phallotoxins) are synthesized on ribosomes. Heather Hallen and Jonathan Walton of Michigan State University, first isolated the genes encoding the proproteins for α-amanitin and phallacidin. == Scientific use == α-Amanitin is an inhibitor of RNA polymerase II and III. This mechanism makes it a deadly toxin. α-Amanitin can also be used to determine which types of RNA polymerase are present. This is done by testing the sensitivity of the polymerase in the presence of α-amanitin. RNA polymerase I is insensitive, RNA polymerase II is highly sensitive (inhibited at 1μg/ml), RNA polymerase III is moderately sensitive (inhibited at 10μg/ml), and RNA polymerase IV is slightly sensitive (inhibited at 50μg/ml). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Alpha-Amanitin」の詳細全文を読む スポンサード リンク
|