Spatial structure of the M2 transmembrane segment of the nicotinic acetylcholine receptor α-subunit

A synthetic peptide corresponding to the transmembrane segment M2 (residues 236–267) of the α-subunit of the nicotinic acetylcholine receptor from Torpedo californica has been studied by two dimensional 1H-NMR spectroscopy in a chloroform-methanol (1:1) mixture containing 0.1 M LiClO4. Reconstruction of the spatial structure of M2 from the NMR data resulted in an α-helix formed by residues 241–263. Distribution of the molecular hydrophobicity potential on the helix surface is very similar to that in five-helix bundles of proteins with a known three dimensional structure: two hydrophilic bands located on the opposite helix sides separated by strong hydrophobic zones.