BotIT2 is a neurotoxin from the scorpion Buthus occitanus tunetanus, which modifies activation and slows down the deactivation of voltage gated sodium channels.
[3] BotIT2 differs from other scorpion toxins not only in its amino acid sequence, but in its effects on activation kinetics of insect sodium channels as well.
Despite 67% homogeneity with BotIT4, BotIT4 can be discriminated from BotIT2, by binding two sodium channel sites and having its exclusive depressant electrophysiological function.
[1][6] BotIT2 binds site 4 of voltage gated sodium channels with low capacity (Bmax = 2.4 ± 0.5 pmol/mg) and high affinity (Kd = 0.3 ± 0.1 nM).
[2][8] Together, BotIT2 modifies the kinetics of insect's sodium channel activation, transforms fast sodium currents in slow current and enhances (in DUM) or induces (in the axon) a repetitive firing pattern or burst activity, but of smaller amplitude.
[1][2][9][8] For instance, injection of BotIT2 into the German cockroach (Blatella Germanica) results in a contraction paralysis effect.
In general, scorpion toxins bind to ion channels via sites of positive surface potential.