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KCa2+ channel blocker

Charybdotoxin (ChTx) is a 37 amino acid peptide isolated from the venom of the scorpion Leiurus quinquestriatus hebraeus that blocks voltage-gated and large conductance Ca2+ activated K+ channels KCa1.1 in nanomolar concentrations (IC50~ 3 nM). 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 KCa3.1 (IC50 5 nM), Kv1.2 (IC50 14 nM), Kv1.3 (IC50 2.6 nM) and Kv1.6 (IC50 2 nM) channels.

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AA sequence: Pyr-Phe-Thr-Asn-Val-Ser-Cys7-Thr-Thr-Ser-Lys-Glu-Cys13-Trp-Ser-Val-Cys17-Gln-Arg-Leu-His-Asn-Thr-Ser-Arg-Gly-Lys-Cys28-Met-Asn-Lys-Lys-Cys33-Arg-Cys35-Tyr-Ser-OH
(Disulfide bonds between Cys7-Cys28, Cys13-Cys33, and Cys17-Cys35)
Length (aa): 37
Formula: C176H277N57O55S7
Molecular Weight: 4295.90 Da
Appearance: White lyophilized solid
Solubility: water and saline buffer
CAS number: 95751-30-7
Source: Synthetic
Purity rate: > 97%


Purification, sequence, and model structure of charybdotoxin, a potent selective inhibitor of calcium-activated potassium channels.

Mechanism of charybdotoxin block of a voltage-gated K+ channel.

The charybdotoxin receptor of a Shaker K+ channel: peptide and channel residues mediating molecular recognition.

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