Purification, characterization and action of two insect toxins from the venom of the scorpion buthotus judaicus

D. Lester*, P. Lazarovici, M. Pelhate, E. Zlotkin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

66 Scopus citations

Abstract

Two toxic proteins, insect toxins I and II, selectively paralytic and lethal to insects, were purified from the venom of the Black scorpion, Buthotus judaicus, using gel permeation and ion-exchange chromatography. Their chemical purity and characteristics were assessed by column chromatography, disc electrophoresis, isoelectrofocusing and amino acid analyses. Their biological specificity and toxicity were determined by a series of paralysis and lethality assays employing the larvae of the flesh fly, Sarcophaga falculata, and the locust, Locust migratoria. Their modes of action were investigated employing in vitro cockroach axonal preparations in current- and voltage-clamp conditions. Insect toxin I (IT-I) is approximately 40-times more toxic than the crude venom (according to its fly larvae paralysing activity), is composed of 67 amino acids including six half cystines, and has an estimated molecular weight of 7532 and a pI value of 8.20. It causes an immediate contraction paralysis of fly larvae and a quick excitatory 'knock-down' effect on locusts. Insect toxin II (IT-II) is about 36-times more toxic than the crude venom according to the paralytic potency in fly larvae. It is composed of 69 amino acids including six half cystines and has an estimated molecular weight of 7894, a unique amino acid composition and a pI value of 8.30. IT-II causes a flaccid paralysis of fly larvae and a slow progressive paralysis and eventually death of locusts. In in vitro current clamp experiments, IT-I induces repetitive activities, and IT-II, a block of the evoked action potentials. These two opposite effects may be explained by their different effects on sodium permeabilities. Both toxins increase the sodium resting permeability (IT-II markedly more) resulting in a progressive depolarization of the axonal membrane. Concerning the activable sodium permeability, both toxins slightly slow the sodium transient inward current turning off. The peak sodium current is increased by IT-I and decreased byIT-II. This essential difference may, at least partially, account for the contrasting symptoms they induce in the whole insect.

Original languageEnglish
Pages (from-to)370-381
Number of pages12
JournalBiochimica et Biophysica Acta - Proteins and Proteomics
Volume701
Issue number3
DOIs
StatePublished - 4 Mar 1982

Keywords

  • (Buthotus judaicus)
  • Neurotoxin
  • Scorpion venom

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