Purification and Molecular Characterization of a Mammalian Neurotoxin as a Pharmaceutical Tool from the Venom of Iranian Scorpion Androctonus crassicauda.

Background: Venom of scorpions are complex bioactive polypeptides. To gain greater insights into the structural and functional impacts of toxins from Androctonus crassicauda (Buthidae), a dangerously venomous scorpion species, its venom was isolated, purified, and characterized.

Methods: Long chain toxin with four disulfide bonds purified by size exclusion chromatography and reversed-phase HPLC and characterized by amino acid sequencing and molecular weight determination.

Results: The primary structure analysis exhibits a neurotoxin named AnCra2 with 7302.24 Da molecular weight and 64 amino acid residues that cause paralysis and lead to death in NIH mice. The LD₅₀ of AnCra2 was determined to be 0.61±0.04 μg/mice. Phylogenetic analysis displays the toxin has 97% sequence similarity with alpha toxins reported from north African scorpions that affect voltage-gated sodium channels (VGSC), also proposed that differentiation among the scorpions of family Buthidae is affected by the geographical conditions and efficiency in evolutionary variations. AnCra2 exposed binding residues have a high affinity for receptor residues in site-3 (segment-3) of VGSC that are approved by three-dimensional structure and homology modeling.

Conclusion: Purified AnCra2 seems to be a new putative Alpha neurotoxin in homology with the structure of neurotoxins that act on VGSC as a pharmaceutical tool.