Heterologous Production and Functional Characterization of Ageritin, a Novel Type of Ribotoxin Highly Expressed during Fruiting of the Edible Mushroom Agrocybe aegerita

Appl Environ Microbiol. 2019 Oct 16;85(21):e01549-19. doi: 10.1128/AEM.01549-19. Print 2019 Nov 1.


Fungi produce various defense proteins against antagonists, including ribotoxins. These toxins cleave a single phosphodiester bond within the universally conserved sarcin-ricin loop of ribosomes and inhibit protein biosynthesis. Here, we report on the structure and function of ageritin, a previously reported ribotoxin from the edible mushroom Agrocybe aegerita The amino acid sequence of ageritin was derived from cDNA isolated from the dikaryon A. aegerita AAE-3 and lacks, according to in silico prediction, a signal peptide for classical secretion, predicting a cytoplasmic localization of the protein. The calculated molecular weight of the protein is slightly higher than the one reported for native ageritin. The A. aegerita ageritin-encoding gene, AaeAGT1, is highly induced during fruiting, and toxicity assays with AaeAGT1 heterologously expressed in Escherichia coli showed a strong toxicity against Aedes aegypti larvae yet not against nematodes. The activity of recombinant A. aegerita ageritin toward rabbit ribosomes was confirmed in vitro Mutagenesis studies revealed a correlation between in vivo and in vitro activities, indicating that entomotoxicity is mediated by ribonucleolytic cleavage. The strong larvicidal activity of ageritin makes this protein a promising candidate for novel biopesticide development.IMPORTANCE Our results suggest a pronounced organismal specificity of a protein toxin with a very conserved intracellular molecular target. The molecular details of the toxin-target interaction will provide important insight into the mechanism of action of protein toxins and the ribosome. This insight might be exploited to develop novel bioinsecticides.

Keywords: GAGA tetraloop; SRL; basidiomycetes; entomotoxicity; gene expression; rRNA; riboendonuclease; ribosome; α-sarcin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agaricales / genetics
  • Agaricales / metabolism*
  • Agrocybe / genetics
  • Agrocybe / metabolism*
  • Amino Acid Sequence
  • Animals
  • Culicidae / drug effects
  • Fungal Proteins / genetics
  • Gene Expression Regulation, Fungal
  • Larva / drug effects
  • Mutagenesis
  • Mutation
  • Mycotoxins / chemistry
  • Mycotoxins / genetics
  • Mycotoxins / metabolism*
  • Mycotoxins / toxicity*
  • Recombinant Proteins
  • Ribonucleases / chemistry
  • Ribonucleases / genetics
  • Ribonucleases / metabolism*
  • Ribonucleases / toxicity*
  • Ribosomes / drug effects
  • Sf9 Cells / drug effects


  • Fungal Proteins
  • Mycotoxins
  • Recombinant Proteins
  • Ribonucleases
  • ageritin