Electrophysiological characterization of BmK M1, an K-like toxin from Buthus martensi Karsch venom

Abstract The present study investigates the electrophysiologi-cal actions of BmK M1, an K-like toxin purified from the venom of the scorpion Buthus martensi Karsch, on voltage-gated Na+ channels. Using the voltage clamp technique, we assessed the BmK M1 activity on the cardiac Na+ channel (hH1) functionally expressed in Xenopus oocytes. The main actions of the toxin are a concentration-dependent slowing of the inactivation process and a hyperpolarizing shift of the steady-state inactivation. This work is the first electrophysiological characterization of BmK M1 on a cloned Na+ channel, demonstrating that this toxin belongs to the class of scorpion K-toxins. Our results also show that BmK M1 can be considered as a cardiotoxin. ß 200