Bot IT sub(2): A new scorpion toxin to study receptor site on insect sodium channels

The insect-specific Buthus occitanus tunetanus IT sub(2) toxin is distinguishable from other scorpion toxins by its amino acid sequence and effects on sodium conductance. The present study reveals that Bot IT sub(2) possesses in cockroach neuronal membranes a single class of high affinity (K sub(d) = 0.3 plus or minus 0.1 nM) and low capacity (B sub(max) = 2.4 plus or minus 0.5 pmol/mg) binding sites. Competitive binding experiments with several known sodium channel neurotoxins reveal that the Bot IT sub(2) binding site is in close proximity to the other toxins.