The reaction site of a non-competitive antagonist in the delta-subunit of the nicotinic acetylcholine receptor.

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Abstract
A site in the primary structure of the nicotinic acetylcholine receptor from Torpedo marmorata covalently labeled with the non‐competitive antagonist [3H]triphenylmethylphosphonium (TPMP+) was localized. The label was found in position 262 of the delta‐polypeptide chain. This site is specifically labeled in the presence of the agonist carbamoylcholine. Labeling is prevented by the non‐competitive antagonist histrionicotoxin. Position 262, probably a serine, is located in the highly conserved membrane‐spanning helix M2 (according to the predicted folding scheme of Finer‐Moore and Stroud (1984). The relationship of this site to the receptor's ion channel and its regulation is discussed.