title: Peptide macrocyclization catalyzed by a prolyl oligopeptidase involved in α-amanitin biosynthesis.
abstract: Amatoxins are ribosomally encoded and posttranslationally modified peptides that account for the majority of fatal mushroom poisonings of humans. A representative amatoxin is the bicyclic octapeptide α-amanitin, formed via head-to-tail macrocyclization, which is ribosomally biosynthesized as a 35-amino acid propeptide in Amanita bisporigera and in the distantly related mushroom Galerina marginata. Although members of the prolyl oligopeptidase (POP) family of serine proteases have been proposed to play a role in α-amanitin posttranslational processing, the exact mechanistic details are not known. Here, we show that a specific POP (GmPOPB) is required for toxin maturation in G. marginata. Recombinant GmPOPB catalyzed two nonprocessive reactions: hydrolysis at an internal Pro to release the C-terminal 25-mer from the 35-mer propeptide and transpeptidation at the second Pro to produce the cyclic octamer. On the other hand, we show that GmPOPA, the putative housekeeping POP of G. marginata, behaves like a conventional POP.
authors.affiliation: Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Luo
authors.affiliation: Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Sung-Yong
authors.initials: SY
authors.lastname: Hong
authors.affiliation: Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA; Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: R Michael
authors.initials: RM
authors.lastname: Sgambelluri
authors.affiliation: Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Evan
authors.initials: E
authors.lastname: Angelos
authors.affiliation: Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Xuan
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA. Electronic address: walton@msu.edu.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Walton
mesh_terms: D053959:Alpha-Amanitin / Q000096:biosynthesis* / Q000737:chemistry; D000545:Amanita / Q000201:enzymology; D000546:Amanitins / Q000096:biosynthesis / Q000737:chemistry; D000595:Amino Acid Sequence; D055162:Biocatalysis; D003500:Cyclization; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D000085822:Prolyl Oligopeptidases; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D013045:Species Specificity
chemical_list: D053959:Alpha-Amanitin; D000546:Amanitins; C018358:phallotoxin; C018207:amatoxin; D012697:Serine Endopeptidases; C000705287:PREPL protein, human; D000085822:Prolyl Oligopeptidases