Ribosomal biosynthesis of the cyclic peptide toxins of Amanita mushrooms
Article first published online: 4 AUG 2010
Copyright © 2010 Wiley Periodicals, Inc.
Special Issue: Special Issue on International Conference on Circular Proteins
Volume 94, Issue 5, pages 659–664, 2010
How to Cite
Walton, J. D., Hallen-Adams, H. E. and Luo, H. (2010), Ribosomal biosynthesis of the cyclic peptide toxins of Amanita mushrooms. Biopolymers, 94: 659–664. doi: 10.1002/bip.21416
- Issue published online: 26 MAY 2010
- Article first published online: 4 AUG 2010
- Manuscript Accepted: 8 FEB 2010
- Manuscript Revised: 6 FEB 2010
- Manuscript Received: 6 JAN 2010
- Michigan State University Plant Research Laboratory, Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy. Grant Number: DE-FG02-91ER20021
- prolyl oligopeptidase;
Some species of mushrooms in the genus Amanita are extremely poisonous and frequently fatal to mammals including humans and dogs. Their extreme toxicity is due to amatoxins such as α- and β-amanitin. Amanita mushrooms also biosynthesize a chemically related group of toxins, the phallotoxins, such as phalloidin. The amatoxins and phallotoxins (collectively known as the Amanita toxins) are bicyclic octa- and heptapeptides, respectively. Both contain an unusual Trp-Cys cross-bridge known as tryptathionine. We have shown that, in Amanita bisporigera, the amatoxins and phallotoxins are synthesized as proproteins on ribosomes and not by nonribosomal peptide synthetases. The proproteins are 34–35 amino acids in length and have no predicted signal peptides. The genes for α-amanitin (AMA1) and phallacidin (PHA1) are members of a large family of related genes, characterized by highly conserved amino acid sequences flanking a hypervariable “toxin” region. The toxin regions are flanked by invariant proline (Pro) residues. An enzyme that could cleave the proprotein of phalloidin was purified from the phalloidin-producing lawn mushroom Conocybe apala. The enzyme is a serine protease in the prolyl oligopeptidase (POP) subfamily. The same enzyme cuts at both Pro residues to release the linear hepta- or octapeptide. © 2010 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 94: 659–664, 2010.
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