Charybdotoxin (trifluoroacetate salt)

Charybdotoxin is a peptide originally isolated from the scorpion L. quinquestriatus that acts as a potassium channel blocker., It blocks large-conductance Ca2+-activated K+ channels (BKCas) in GH3 rat pituitary tumor cells and primary bovine aortic smooth muscle cells (Kds = 2.1 and ~2.1 nM, respectively). Charybdotoxin selectively blocks voltage-gated potassium (Kv) channels Kv1.2 and Kv1.3 over Kv1.1, Kv1.5, and Kv3.1 (Kds = 14, 2.6, >1,000, >100, >1,000 nM, respectively). It also blocks human large-conductance pH-activated potassium channel KCa5.1 (Slo3) by 47% at a concentration of 100 nM and pH of 7.4, and human intermediate-conductance Ca2+-activated K+ channel IKCa1/KCa3.1 (Kd = 10 nM).,