The gene encoding the Bm alpha TX14 (alpha-neurotoxin TX14) protein, derived from the cDNA library of the Chinese scorpion Buthus martensii Karsch, was expressed in Pichia pastoris. The recombinant protein was purified by metal chelate affinity chromatography and gel filtration chromatography. Using patch-clamp technique, electrophysiological activity of rBm alpha TX14 was identified. In the neurons isolated from mice trigeminal root ganglion, the Na+ current amplitude was reduced by 80% under whole cell patch-clamp recording. There were no apparent modifications to the gating mechanism in the presence of rBm alpha TX14. Although Bm alpha TX14 shared a high amino acid sequence similarity with other typical alpha-toxins, it has different effects on neurons. Further electrophysiological analysis suggested that rBm alpha TX14 selectively blocked Na+ channels and is a member of a new group of scorpion toxins.