Hongotoxin
# 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. $HgTX_1$ 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.

$HgTX_1$ 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).

$HgTX_2,$ $HgTX_3,$ $HgTX_4$ and $HgTX_5$ are potent selective inhibitors of Kv1 voltage-gated potassium channels (By similarity).

| table 1 | | $IC_{50}$ | | |
| - | - | - | - | - |
| | $K_v1.1$ | $K_v1.2$ | $K_v1.3$ | $K_v1.6$ |
| $HgTX_1$ | 31 | 170 | 86 | 6,000 |
| MgTx | 144 | 675 | 230 | ND |

ND, not determined. All measurements in pM

| table 2 | | $K_i$ | | |
| - | - | - | - | - |
| | $K_v1.1$ | $K_v1.2$ | $K_v1.3$ | $K_v1.6$ |
| $HgTX_1$ | 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.

