The snake toxin is one of a family of
small neurotoxic proteins (MW ～ 8,000 Da) isolated from
the venom of elapid snakes (cobras and their relatives).
α-Bungarotoxin also binds to certain insect nAChRs (8,9),
although a separate α-bungarotoxin–insensitive class of
nAChR has been found in some species (9).
The snake toxin,
α-bungarotoxin, has been used extensively to characterize
vertebrate nAChRs because it selectively binds to certain
populations of vertebrate receptors.
The snake toxin binds
very tightly to the receptor and competitively blocks
the binding of acetylcholine; consequently, radiolabeled
α-bungarotoxin has been used to design competitive binding
assays to measure the in vitro potencies of competitive
ligands such as the neonicotinoids. However, no information
concerning the agonist or antagonist nature of
test compounds is obtained using these methods.
Binding
studies using both α-bungarotoxin and imidacloprid have
indicated that some insect receptors that do not bind α-
bungarotoxin with high affinity do bind imidacloprid (10).
Such bungarotoxin-insensitive nicotinic receptors have
also been identified using electrophysiology (11).
