Alpha-scorpion neurotoxin derivatives suitable as potential markers of sodium channels. Preparation and characterization.

Modified scorpion neurotoxins, i.e. mono-biotinylated and mono-azido derivatives either on lysine 58 or lysine 60 have been characterized both at the structural level (sequence and circular dichroism) and by their pharmacological activity (toxicity to mice and ability to displace 125I-Androctonus australis Hector toxin II from its receptor sites. The results allowed us to pinpoint a region of the molecule including lysine residues 58 and 60 that is important for neurotoxin receptor interaction. Furthermore, as these derivatives retain, after 125I labeling, high binding capacities to synaptosomal membranes, they can be used as potential labels of the sodium channel either by covalent binding or using the avidin-biotin system.