Charybdotoxin

Charybdotoxin is a 37 amino acid peptide isolated from the venom of the scorpion Leiurus quinquestriatus hebraeus that blocks voltage gated and Ca2+ activated K+ channels. This blockade causes hyperexcitability of the nervous system. The toxin reversibly blocks channel activity by interacting at the external pore of the channel protein with an apparent Kd of 2.1 nM. ChTX also blocks Kv1.2 (Kd 14 nM) and Kv1.3 (Kd 2.6nM) channels.