Hongotoxin

Hongotoxin (HgTX) is an ion channel toxin, which blocks Shaker-type (K_v1) 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 (K_v1) K⁺ channels.

HgTX₁ shows high affinity with K_v1.1, K_v1.2, K_v1.3 voltage-gated potassium channels, but much lower affinity with K_v1.6 (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.^{[ citation needed ]}

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

External links

• 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.