Charybdotoxin

Charybdotoxin (CTX) is a 37 amino acid neurotoxin from the venom of the scorpion Leiurus quinquestriatus hebraeus that blocks calcium-activated potassium channels. This blockade causes hyperexcitability of the nervous system.

Chemical properties
Scorpions such as the deathstalker paralyse their prey by injecting a potent mix of peptide toxins. Charybdotoxin (CTX), a 37 amino acid neurotoxin, is one of the peptide toxins that can be extracted from the venom of the scorpion. Its structure is very similar to that of margatoxin. Charybdotoxin contains three disulfide bridges.

Mode of action
Charybdotoxin occludes the pore of calcium-activated voltage-gated K+ channels by binding to one of four independent, overlapping binding sites. It binds both to the open and the closed states. In addition, the block is enhanced as the ionic strength is lowered. The blockade of K+ channels by the charybdotoxin peptide causes neuronal hyperexcitability.

Treatment
Anti-scorpion venom serum (AScVS) is an effective and safe method of therapy in severe scorpion envenoming syndrome. Compared with other therapies like alpha blockers it has a relatively short recovery period (10 vs 16-42 hours).