Mechanisms Underlying the Inhibition of KV1.3 Channel by Scorpion Toxin ImKTX58.

Voltage-gated K1.3 channel has been reported to be a drug target for the treatment of autoimmune diseases, and specific inhibitors of Kv1.3 are potential therapeutic drugs for multiple diseases. The scorpions could produce various bioactive peptides that could inhibit K1.3 channel. Here, we identified a new scorpion toxin polypeptide gene from the venom gland cDNA library of the Chinese scorpion Sequence alignment revealed high similarities between mature peptide and previously reported K1.3 channel blockers-LmKTX10 and ImKTX88-suggesting that ImKTX58 peptide might also be a K1.3 channel blocker. By using electrophysiological recordings, we showed that recombinant ImKTX58 prepared by genetic engineering technologies had a highly selective inhibiting effect on K1.3 channel. Further alanine scanning mutagenesis and computer simulation identified four amino acid residues in ImKTX58 peptide as key binding sites to K1.3 channel by forming hydrogen bonds, salt bonds, and hydrophobic interactions. Among these four residues, 28th lysine of the ImKTX58 mature peptide was found to be the most critical amino acid residue for blocking K1.3 channel. SIGNIFICANCE STATEMENT: In this study, we discovered a scorpion toxin gene that has not been reported before in Hainan and successfully used the prokaryotic expression system to express and purify the polypeptides encoded by this gene. Electrophysiological experiments on ImKTX58 showed that ImKTX58 has a highly selective blocking effect on K1.3 channel over Kv1.1, Kv1.2, Kv1.5, SK2, SK3, and BK channels. These findings provide a theoretical basis for designing highly effective K1.3 blockers to treat autoimmune and other diseases.