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
editHongotoxin 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
editHongotoxin (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
editThe mode of action is not yet known.[citation needed]
References
edit- ^ a b c d 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.
- ^ Rein, Jan Ove. "Centruroides limbatus". The Scorpion Files.
- ^ Hongotoxin-2
- ^ Hongotoxin-3
- ^ Hongotoxin-4
- ^ Hongotoxin-5
External links
edit- 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.