Phaiodotoxin, a novel structural class of insect-toxin isolated from the venom of the Mexican scorpion Anuroctonus phaiodactylus

Norma A. Valdez-Cruz, Cesar V.F. Batista, Fernando Z. Zamudio, Frank Bosmans, Jan Tytgat, Lourival D. Possani

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


A peptide called phaiodotoxin was isolated from the venom of the scorpion Anuroctonus phaiodactylus. It is lethal to crickets, but non toxic to mice at the doses assayed. It has 72 amino acid residues, with a molecular mass of 7971 atomic mass units. Its covalent structure was determined by Edman degradation and mass spectrometry; it contains four disulfide-bridges, of which one of the pairs is formed between cysteine-7 and cysteine-8 (positions Cys63-Cys71). The other three pairs are formed between Cys13-Cys38, Cys23-Cys50 and Cys27-Cys52. Comparative sequence analysis shows that phaiodotoxin belongs to the long-chain subfamily of scorpion peptides. Several genes coding for this peptide and similar ones were cloned by PCR, using cDNA prepared from the RNA of venomous glands of this scorpion. Electrophysiological assays conducted with this toxin in several mammalian cell fines (TE671, COS7, rat GH3 and cerebellum granular cells), showed no effect on Na+ currents. However, it shifts the voltage dependence of activation and inactivation of insect Na+ channels (para/tipE) to more negative and positive potentials, respectively. Therefore, the 'window' current is increased by 225%, which is thought to be the cause of its toxicity toward insects. Phaiodotoxin is the first toxic peptide ever purified from a scorpion of the family Iuridae.

Original languageEnglish (US)
Pages (from-to)4753-4761
Number of pages9
JournalEuropean Journal of Biochemistry
Issue number23-24
StatePublished - Dec 2004
Externally publishedYes


  • Anuroctonus phaiodactylus
  • Disulfide bridges
  • Insect toxin
  • Na -channel
  • Scorpion

ASJC Scopus subject areas

  • Biochemistry


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