Purification, characterization and molecular modelling of two toxin-like proteins from the Androctonus australis Hector venom

Two toxin-like proteins (AahTL1 and AahTL3) were purified from the venom of the scorpion Androctonus australis Hector (Aah). AahTL1 and AahTL3 are the first non toxic proteins cross-reacting with AahI toxins group which indic ates that these proteins can be used as a model of vaccins. In order to study structure-function relationships, their complete amino-ac id sequences (66 residues) were determined, by automated Edman degradation. They show more than 50% of similarity with both AahI and AahIII antimammal toxins. Three-dimensional structural models of AahTL1 and AahTL3 construct ed by homology suggest that the two proteins are structurally similar to an timammal scorpion alpha-toxins specific to voltage dependent Na+ channels. The models showed also that amino-acid changes between potent Aah toxins an d both AahTL1 and AahTL3 disrupt the electrostatic potential gradient at th eir surface preventing their interaction with the receptor, which may expla in their non toxicity.