Molecular basis of Tityus stigmurus alpha toxin and potassium channel kV1.2 interactions.

The Tityus stigmurus scorpion is widely distributed in the Northeast of Brazil and is the main causal agent of human envenoming. The venom produced by this scorpion includes neurotoxins, which are peptides belonging to Family 2 toxins and are able to interact with ion channels. The KTx subfamily displays selectivity and affinity for Kv channel subtypes and the result of this interaction is the blockade of potassium channels, impairing vital functions. We report the optimized structural model of a transcript encoding a potassium channel blocker toxin from T. stigmurus. LC-MS analysis confirmed the presence of the toxin in the venom and the three-dimensional structure was obtained by computational homology modeling and refined by molecular dynamic simulations. Furthermore, docking simulations were performed using a Shaker kV-1.2 potassium channel from rats as receptor model and the contacts were identified revealing which amino acid residues and interactions could be involved in its blockade. These residues were mapped and their contact and electrostatic interactions were evaluated revealing the influence of positive lysine residues and the additional contribution of an asparagine to the stabilization of the complex, bringing new insights into the mechanism of action of this toxin.