Destruction of acetylcholine receptor by decaying 125I-alpha-bungarotoxin.

Decay of 125I in 125I-alpha-bungarotoxin bound to detergent-solubilized acetylcholine receptor from Torpedo californica electric tissue results in the inactivation of virtually all of the directly occupied and of the second toxin-binding sites. This finding establishes the usefulness of 125I-labeled ligands for binding-site multiplicity analysis of proteins.