A proposal for the structure of conotoxin--a potent antagonist of the nicotinic acetylcholine receptor.

Conotoxin, a thirteen residue neurotoxic peptide, is demonstrated, by circular dichroism measurements, to possess a high content of alpha-helix. The location of this helix in the sequence is severely limited by the structural preferences of individual amino acids and by the positioning of the two cystine links. Comparisons are made between the reactive site of elapidae snake venom postsynaptic neurotoxins and the surface of the conotoxin molecule.