Phaiodotoxin, a novel structural class of insect-toxin isolated from the venom of the Mexican scorpion Anuroctonus phaiodactylus
Por:
Valdez-Cruz N.A., Batista C.V.F., Zamudio F.Z., Bosmans F., Tytgat J., Possani L.D.
Publicada:
1 ene 2004
Resumen:
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.
Filiaciones:
Valdez-Cruz N.A.:
Dept. of Molec. Med. and Bioproc., Institute of Biotechnology, Natl. Autonomous Univ. of Mexico, Cuernavaca, Mexico
Batista C.V.F.:
Dept. of Molec. Med. and Bioproc., Institute of Biotechnology, Natl. Autonomous Univ. of Mexico, Cuernavaca, Mexico
Zamudio F.Z.:
Dept. of Molec. Med. and Bioproc., Institute of Biotechnology, Natl. Autonomous Univ. of Mexico, Cuernavaca, Mexico
Bosmans F.:
Laboratory of Toxicology, University of Leuven, Leuven, Belgium
Tytgat J.:
Laboratory of Toxicology, University of Leuven, Leuven, Belgium
Possani L.D.:
Dept. of Molec. Med. and Bioproc., Institute of Biotechnology, Natl. Autonomous Univ. of Mexico, Cuernavaca, Mexico
Instituto de Biotecnologia UNAM, Avenida Universidad, 2001, Cuernavaca 62210, Mexico
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