On the Interaction between Cobra -Neurotoxin and the Acetylcholine Receptor

Elapid α-neurotoxins bind specifically to recognition sites of nicotinic receptors. The high affinity and slow reversibility of this interaction have made these toxins especially useful as labeling reagents for the isolation, purification and assay of nicotinic receptor proteins. Quantitative analysis of receptor-ligand interactions performed as competition binding studies with radioactively labeled α-neurotoxin (Maelicke et al. 1976) now shows that this group of small proteins forms a distinct class of ligands different from low molecular weight agonists and antagonists. Therefore a detailed description of the receptor-toxin interaction might provide insights into the principle of ligand-binding and coupled molecular events. Since this is an interaction between a small protein and a membrane receptor, it might serve, in addition, as a model system for certain aspects of hormone-receptor interactions.