An anti-insect toxin purified from the scorpion Androctonus australis Hector also acts on the .alpha.- and .beta.-sites of the mammalian sodium channel: sequence and circular dichroism study

A new anti-insect neurotoxin, AaH IT4, has been isolated from the venom of the North African scorpion Androctonus australis Hector. This polypeptide has a toxic effect on insects and mammals and is capable of competing with anti-insect scorpion toxins for binding to the sodium channel of insects; it...

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Bibliographic Details
Published in:Biochemistry (Easton) 1991-01, Vol.30 (3), p.633-640
Main Authors: Loret, Erwann P, Martin-Eauclaire, Marie France, Mansuelle, Pascal, Sampieri, Francois, Granier, Claude, Rochat, Herve
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Androctonus australis
Animal poisons toxicology. Antivenoms
Animals
Binding, Competitive
Biological and medical sciences
Buthidae
Circular Dichroism
DOSAGE BIOLOGIQUE
ENSAYO BIOLOGICO
Medical sciences
Molecular Sequence Data
Neuropeptides - chemistry
Neurotoxins - chemistry
Protein Conformation
PURIFICACION
PURIFICATION
SARCOPHAGIDAE
Scorpion Venoms - chemistry
SCORPIONES
Scorpions - analysis
SISTEMA NERVIOSO
Sodium Channels - chemistry
SYSTEME NERVEUX
TOXICIDAD
TOXICITE
Toxicology
TOXINAS
TOXINE
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Summary:A new anti-insect neurotoxin, AaH IT4, has been isolated from the venom of the North African scorpion Androctonus australis Hector. This polypeptide has a toxic effect on insects and mammals and is capable of competing with anti-insect scorpion toxins for binding to the sodium channel of insects; it also modulates the binding of alpha-type and beta-type anti-mammal scorpion toxins to the mammal sodium channel. This is the first report of a scorpion toxin able to exhibit these three kinds of activity. The molecule is composed of 65 amino acid residues and lacks methionine and, more unexpectedly, proline, which until now has been considered to play a role in the folded structure of all scorpion neurotoxins. The primary structure showed a poor homology with the sequences of other scorpion toxins; however, it had features in common with beta-type toxins. In fact, radioimmunoassays using antibodies directed to scorpion toxins representative of the main structural groups showed that there is a recognition of AaH IT4 via anti-beta-type toxin antibodies only. A circular dichroism study revealed a low content of regular secondary structures, particularly in beta-sheet structures, when compared to other scorpion toxins. This protein might be the first member of a new class of toxins to have ancestral structural features and a wide toxic range
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00217a007