Site-directed mutagenesis of the toxin from the Chinese scorpion Buthus martensii Karsch (BmKAS): insight into sites related to analgesic activity.

This study utilized the E. coli expression system to investigate the role of amino acid residues in toxin from the Chinese scorpion--Buthus martensii Karsch (BmKAS). To evaluate the extent to which residues of the toxin core contribute to its analgesic activity, ten mutants of BmKAS were obtained by PCR. Using site-directed mutagenesis, all of these residues were substituted with different amino acids. This study represents a thorough mapping and elucidation of the epitopes that form the molecular basis of the toxin's analgesic activity. Our results showed large mutant-dependent differences that emphasize the important roles of the studied residues.