Kaliotoxin
Kaliotoxin (KTX) inhibits potassium flux through the Kv1.3 voltage-gated potassium channel and calcium-activated potassium channels by physically blocking the channel-entrance and inducing a conformational change in the K+-selectivity filter of the channel. Sources KTX is a neurotoxin derived from the scorpion Androctonus mauretanicus mauretanicus, which is found in the Middle East and North Africa. (Crest M et al.) Chemistry Kaliotoxin is a 4-kDa polypeptide chain, containing 38 amino acids. The formula is C171H283N55O49S8. The sequence has a large homology with iberiotoxin from Buthus tumulus, charybdotoxin from Leiurus quinquestriatus and noxiustoxin from Centruroides noxius. An Important site of the toxin is the K27 side chain (a lysine at place 27 of the protein sequence), which enters the pore and protrudes into the selectivity filter of the channel. (Lange A et al., Korukottu J et al.) Target KTX binds to the Kv1.3 voltage-gated potassium channel and the Calcium-activated potassium channels (BK channels). (Lange A et al., Crest M et al., Zachariae U et al., Aiyar J et al.,) These channels control several regulating processes, including neurotransmitter release, heart rate, insulin secretion, smooth muscle contraction. (Wickenden A et al.) Kv1.3 channels also play a critical role in regulating the function of effector memory