Photolabeling reveals the proximity of the a-neurotoxin binding site to the M2 helix of the ion channel in the nicotinic acetylcholine receptor
Machold, J.; Utkin, Y.; Kirsch, D.
Proceedings of the National Academy of Sciences of the United States of America 92: 82-6
1995
ISSN/ISBN: 0027-8424
Accession: 009938666
The architecture of the agonist/competitive antagonist binding site environment in the nicotinic acetylcholine receptor (AChR) was probed photochemically. The probe used was a photoactivatable derivative of Naja naja oxiana neurotoxin II that contained a 125I-labeled p-azidosalicylamidoethyl-1,3'-dithiopropyl at Lys-25. The a-neurotoxin cross-linked with AChR at a site in the upper part of the channel-forming transmembrane helix M2, demonstrating that the center of the a-neurotoxin binding site is at least about 40 A from the extracellular surface of the receptor and proximal to the channel axis.