Exposure of acetylcholine receptor to the lipid bilayer.

All four subunits of the acetylcholine receptor in membrane fragments isolated from T. californica have been labeled with a photolabile hydrophobic probe, [3H]adamantanediazirine, which selectively labels regions of integral membrane proteins in contact with the hydrocarbon core of the lipid bilayer. As all of the homologous subunits are exposed to the lipid bilayer, it is probable that they each interact with the surrounding membrane in a similar fashion.