Molecular analysis of the sea anemone toxin Av3 reveals selectivity to insects and demonstrates the heterogeneity of receptor site-3 on voltage-gated Na+ channels

Yehu Moran, Roy Kahn, Lior Cohen, Maya Gur, Izhar Karbat, Dalia Gordon*, Michael Gurevitz

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

Abstract

Av3 is a short peptide toxin from the sea anemone Ammonia viridis shown to be active on crustaceans and inactive on mammals. It inhibits inactivation of Navs (voltage-gated Na+ channels) like the structurally dissimilar scorpion α-toxins and type I sea anemone toxins that bind to receptor site-3. To examine the potency and mode of interaction of Av3 with insect Navs, we established a system for its expression, mutagenized it throughout, and analysed it in toxicity, binding and electrophysiological assays. The recombinant Av3 was found to be highly toxic to blowfly larvae (ED50 = 2.65 ± 0.46 pmol/100 mg), to compete well with the site-3 toxin LqhαIT (from the scorpion Leiurus quinquestriatus) on binding to cockroach neuronal membranes (Ki = 21.4 ± 7.1 nM), and to inhibit the inactivation of Drosophila melanogaster channel, DmNav1, but not that of mammalian Navs expressed in Xenopus oocytes. Moreover, like other site-3 toxins, the activity of Av3 was synergically enhanced by ligands of receptor site-4 (e.g. scorpion β-toxins). The bioactive surface of Av3 was found to consist mainly of aromatic residues and did not resemble any of the bioactive surfaces of other site-3 toxins. These analyses have portrayed a toxin that might interact with receptor site-3 in a different fashion compared with other ligands of this site. This assumption was corroborated by a D1701R mutation in DmNav1, which has been shown to abolish the activity of all other site-3 ligands, except Av3. All in all, the present study provides further evidence for the heterogeneity of receptor site-3, and raises Av3 as a unique model for design of selective anti-insect compounds.

Original languageAmerican English
Pages (from-to)41-48
Number of pages8
JournalBiochemical Journal
Volume406
Issue number1
DOIs
StatePublished - 15 Aug 2007
Externally publishedYes

Keywords

  • Av3 toxin
  • Insecticidal toxin
  • Receptor site-3
  • Sea anemone
  • Voltage-gated sodium channel (Na)

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