Phaiodotoxin

Phaiodotoxin acts on voltage-dependent sodium ion channels of insects. It shifts the voltage dependent activation curve to more negative values. In addition, the steady-state inactivation curve is shifted to more positive potentials. As a result, smaller depolarizations are needed for the channel to open, and the channel will need larger depolarizations to inactivate. These two effects increase the so-called window current, a measure for the non-inactivating fraction of the sodium currents, by 225%. Phaiodotoxin thus combines the actions of α-scorpion toxins (slowed inactivation) and β-scorpion toxins (enhanced activation). This dual action may be explained by the homology of Phaiodotoxin to both types of scorpion toxins.

Studies in different cell lines indicate that Phaiodotoxin does not affect mammalian sodium channels. Furthermore, there are no accidents of intoxication reported after stings of the Mafia scorpion, suggesting that phaiodotoxins are insect-specific. In crickets 0.8-1.0 μg of phaiodotoxin can result in flaccidity, impairment of movements, paralysis and death.