Functional site of bukatoxin, an α-type sodium channel neurotoxin from the Chinese scorpion (Buthus martensi Karsch) venom: Probable role of the 52PDKVP56 loop

Abstract

α-Toxins from scorpion venoms prolong the action potential of excitable cells by blocking sodium channel inactivation. We have purified bukatoxin, an α-toxin from scorpion (Buthus martensi Karsch) venom, to homogeneity. Bukatoxin produced marked relaxant responses in the carbachol-precontracted rat anococcygeus muscle (ACM), which were mediated through the L-arginine-nitric oxide synthase-nitric oxide pathway, consequent to a neuronal release of nitric oxide. Based on the presence of proline residues in the flanking segments of protein-protein interaction sites, we predicted the site between 52PP56 to be the potential interaction site of bukatoxin. A homology model of bukatoxin indicated the presence of this site on the surface. Buka11, a synthetic peptide designed based on this predicted site, produced a concentration-dependent nitric oxide-mediated relaxant response in ACM. Using alanine-substituted peptides, we have shown the importance 53DKV55 flanked by proline residues in the functional site of bukatoxin. © 2001 Federation of European Biochemical Societies.