Chemistry:Hemitoxin
Hemitoxin (HTX; α-KTx6.15) is a 35-mer basic peptide from the venom of the Iranian scorpion Hemiscorpius lepturus, which reversibly blocks Kv1.1, Kv1.2 and Kv1.3 voltage-gated K+ channels.[1]
Sources
HTX is a neurotoxin derived from the venom of the scorpion Hemiscorpius lepturus, which is found in the southwest province of Iran, Khuzestan. Hemitoxin constitutes about 0.1% of all venom proteins found in the Hemiscorpius lepturus venom gland.[1]
Chemistry
HTX is a peptide composed of 35 amino acids including eight cysteine residues which are cross linked forming four intramolecular cystine amino acids via disulfide bridges. It belongs to subfamily 6 of the α-KTx family of potassium channel scorpion toxins and has the highest sequence similarity with Maurotoxin (MTX), which is derived from a Tunisian scorpion called Scorpio maurus palmatus. MTX is also a K+ channel blocker but is composed of 34 amino acids instead of 35.[1]
Target
HTX is a voltage-gated K+ channel blocker peptide. It reversibly blocks type Kv1.1, Kv1.2 and Kv1.3 channels with IC50 values of 13, 16 and 2 nM, respectively. HTX has a different affinity for K+ channels. It appears to be 20 times less potent on Kv1.2 channels and 90 times more potent on Kv1.3 channels than the α-KTx6 family member MTX.[1]
Mode of Action
HTX causes reversible current inhibition on Kv1.1, Kv1.2 and Kv1.3 channels.[1]
Toxicity
Intracerebroventricular injection of HTX has been shown to cause neurotoxic symptoms in mice with an LD50 of 0.3 μg per 20 g body weight.[1]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Srairi-Abid, N.; Shahbazzadeh, D.; Chatti, I.; Mlayah-Bellalouna, S.; Mejdoub, H.; Borchani, L.; Benkhalifa, R.; Akbari, A. et al. (2008). "Hemitoxin, the first potassium channel toxin from the venom of the Iranian scorpion Hemiscorpius lepturus". FEBS Journal 275 (18): 4641–4650. doi:10.1111/j.1742-4658.2008.06607.x. PMID 18699777.
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