Affinity-directed crosslinking of membrane-bound acetylcholine receptor polypeptides with photolabile .alpha.-bungarotoxin derivatives

Abstract

Photolabile derivatives of [125I]-.alpha.-bungarotoxin that retain specific binding to Torpedo californica acetylcholine receptor were utilized as structural probes of the receptor complex of polypeptide components in its membrane-associated form. The derivatized toxins contained aryl azide side chains poised to form covalent cross-links to both associated and adjacent polypeptides following to toxin-receptor complex formation. Depending on the possible radius of extension of the photoactivated group from the parent toxin, either the polypeptide to which the toxin derivative binds and an adjacent polypeptide can be derivatized upon photolysis, or only the adjacent polypeptide is labeled. The nicotinic receptor from T. california is probably composed of a complex of different polypeptides.