OD1, the first toxin isolated from the venom of the scorpion Odonthobuthus doriae active on voltage-gated Na+ channels

In this study, we isolated and pharmacologically characterized the first α-like toxin from the venom of the scarcely studied Iranian scorpion Odonthobuthus doriae. The toxin was termed OD1 and its primary sequence was determined: GVRDAYIADDKNCVYTCASNGYCNTECTKNGAESGYCQWIGRYGNACWCIKLPDEVPIRIPGKCR. Using the two-electrode voltage clamp technique, the pharmacological effects of OD1 were studied on three cloned voltage-gated Na+ channels expressed in Xenopus laevis oocytes (Nav1.2/β1, Nav1.5/β1, para/tipE). The inactivation process of the insect channel, para/tipE, was severely hampered by 200 nM of OD1 (EC50 = 80 ± 14 nM) while Nav1.2/β1 still was not affected at concentrations up to 5 μM. Nav1.5/β1 was influenced at micromolar concentrations.