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. 1 2 3 4 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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