Hongotoxin

Hongotoxin (HgTX) is an ion channel toxin, which blocks Shaker-type (Kv1) K+ channels. The toxin is derived from the venom of Centruroides limbatus,[1] a Central American scorpion found meanly in Costa Rica, Honduras and Panama.[2]

Chemistry

Hongotoxin belongs to the short scorpion toxin superfamily. Potassium channel inhibitor family. Alpha-KTx 2 subfamily.[1]

There are five subtypes known of the hongotoxin peptide. HgTX1 is 39 amino acids long and shows an overall amino acid sequence homology of 89% to margatoxin (MgTX).[1]

Target

Hongotoxin (HgTX) targets are Shaker-type (Kv1) K+ channels.

HgTX1 shows high affinity with Kv1.1, Kv1.2, Kv1.3 voltage-gated potassium channels, but much lower affinity with Kv1.6 (see table 1 and 2[1]).

HgTX2,[3] HgTX3,[4] HgTX4[5] and HgTX5[6] are potent selective inhibitors of Kv1 voltage-gated potassium channels (By similarity).

table 1 IC50
Kv1.1 Kv1.2 Kv1.3 Kv1.6
HgTX1 31 170 86 6,000
MgTx 144 675 230 ND

ND, not determined. All measurements in pM

table 2 Ki
Kv1.1 Kv1.2 Kv1.3 Kv1.6
HgTX1 0.08 0.09 0.24 8.7
MgTx 0.52 0.21 0.31 9.4

All measurements in pM

Mode of action

The mode of action is not yet known.

References
  1. Koschak A, Bugianesi RM, Mitterdorfer J, Kaczorowski GJ, Garcia ML, Knaus HG (January 1998). "Subunit composition of brain voltage-gated potassium channels determined by hongotoxin-1, a novel peptide derived from Centruroides limbatus venom". The Journal of Biological Chemistry. 273 (5): 2639–44. doi:10.1074/jbc.273.5.2639. PMID 9446567.
  2. Rein, Jan Ove. "Centruroides limbatus". The Scorpion Files.
  3. Hongotoxin-2
  4. Hongotoxin-3
  5. Hongotoxin-4
  6. Hongotoxin-5
  • Pragl B, Koschak A, Trieb M, et al. (2002). "Synthesis, characterization, and application of cy-dye- and alexa-dye-labeled hongotoxin(1) analogues. The first high affinity fluorescence probes for voltage-gated K+ channels". Bioconjugate Chemistry. 13 (3): 416–25. doi:10.1021/bc015543s. PMID 12009929.
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