Chemistry: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, a Central American scorpion found meanly in Costa Rica, Honduras and Panama.

Chemistry

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

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).

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).

HgTX₂, HgTX₃, HgTX₄ and HgTX₅ 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.

External links

• "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. 2002. doi:10.1021/bc015543s. PMID 12009929.