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Charybdotoxin (CTX) is a 37 amino acid neurotoxin from the venom of the scorpion Leiurus quinquestriatus hebraeus that blocks calcium-activated potassium channels.1 This blockade causes hyperexcitability of the nervous system.
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Chemical properties
Scorpions such as the deathstalker paralyse their prey by injecting a potent mix of peptide toxins2. 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 bridges3.
Mode of action
Charybdotoxin occludes the pore of calcium-activated voltage-gated K+ channels by binding to one of four independent, overlapping binding sites45. It binds both to the open and the closed states. In addition, the block is enhanced as the ionic strength is lowered.6 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).7
References
- ^ Laurent F, Michel A, Bonnet PA, Chapat JP, Boucard M (March 1993). "Evaluation of the relaxant effects of SCA40, a novel charybdotoxin-sensitive potassium channel opener, in guinea-pig isolated trachealis". Br. J. Pharmacol. 108 (3): 622–6. PMID 7682131.
- ^ Purves D, Augustine GJ, Fitzpatrick D, Hall WC, Lamantia AS, McNamara JO, Williams SM. Neuroscience, p82.
- ^ Avdonin V, Nolan B, Sabatier JM, Waard M de, Hoshi T, Mechanisms of Maurotoxin Action on Shaker Potassium Channels, Biophys J. 2000 August; 79: 776–787. [1]
- ^ Thompson J, Begenisich T, Electrostatic interaction between charbotoxin and a tetrameric mutant of Shaker K+ channels, Biophys J. 2000 May; 78(5): 2382-91. [2]
- ^ Naranjo D, Miller C, A strongly interacting pair of residues on the contact surface of charybdotoxin and a Shaker K+ channel, Neuron. 1996 Jan; 16(1): 123-30. [3]
- ^ MacKinnon R, Reinhart PH, White MM (December 1988). "Charybdotoxin block of Shaker K+ channels suggests that different types of K+ channels share common structural features". Neuron 1 (10): 997–1001. PMID 2483094, http://linkinghub.elsevier.com/retrieve/pii/0896-6273(88)90156-0.
- ^ Natu VS, Murthy RK, Deodhar KP (April 2006). "Efficacy of species specific anti-scorpion venom serum (AScVS) against severe, serious scorpion stings (Mesobuthus tamulus concanesis Pocock)--an experience from rural hospital in western Maharashtra". J Assoc Physicians India 54: 283–7. PMID 16944610.
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