title: Gene family encoding the major toxins of lethal Amanita mushrooms.
abstract: Amatoxins, the lethal constituents of poisonous mushrooms in the genus Amanita, are bicyclic octapeptides. Two genes in A. bisporigera, AMA1 and PHA1, directly encode alpha-amanitin, an amatoxin, and the related bicyclic heptapeptide phallacidin, a phallotoxin, indicating that these compounds are synthesized on ribosomes and not by nonribosomal peptide synthetases. alpha-Amanitin and phallacidin are synthesized as proproteins of 35 and 34 amino acids, respectively, from which they are predicted to be cleaved by a prolyl oligopeptidase. AMA1 and PHA1 are present in other toxic species of Amanita section Phalloidae but are absent from nontoxic species in other sections. The genomes of A. bisporigera and A. phalloides contain multiple sequences related to AMA1 and PHA1. The predicted protein products of this family of genes are characterized by a hypervariable "toxin" region capable of encoding a wide variety of peptides of 7-10 amino acids flanked by conserved sequences. Our results suggest that these fungi have a broad capacity to synthesize cyclic peptides on ribosomes.
authors.affiliation: Department of Plant Biology and U.S. Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA. hallenhe@msu.edu
authors.forename: Heather E
authors.initials: HE
authors.lastname: Hallen
authors.forename: Hong
authors.initials: H
authors.lastname: Luo
authors.forename: John S
authors.initials: JS
authors.lastname: Scott-Craig
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Walton
mesh_terms: D000545:Amanita / Q000235:genetics*; D000546:Amanitins / Q000096:biosynthesis / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D001487:Basidiomycota / Q000201:enzymology / Q000235:genetics; D017124:Conserved Sequence; D005656:Fungal Proteins / Q000235:genetics; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D005810:Multigene Family; D010456:Peptides, Cyclic / Q000096:biosynthesis / Q000737:chemistry; D000085822:Prolyl Oligopeptidases; D017434:Protein Structure, Tertiary; D012270:Ribosomes / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000235:genetics; D013045:Species Specificity
chemical_list: D000546:Amanitins; D005656:Fungal Proteins; D010456:Peptides, Cyclic; C018358:phallotoxin; C018207:amatoxin; D012697:Serine Endopeptidases; D000085822:Prolyl Oligopeptidases