The αm1 segment of the nicotinic acetylcholine receptor exhibits conformational flexibility in a membrane environment

Abstract

The transmembrane domain of the nicotinic acetylcholine receptor (nAChR) is predominantly α-helical, and of the four distinctly different transmembrane M-segments, only the helicity of M1 is ambiguous. In this study, we have investigated the conformation of a membrane-embedded synthetic M1 segment by solid-state nuclear magnetic resonance (NMR) methods. A 35-residue peptide representing the extended αM1 domain 206-240 of the Torpedo californica nAChR was synthesized with specific 13C- and 15N-labelled amino acids, and was incorporated in different phosphatidylcholine model membranes. The chemical shift of the isotopic labels was resolved by magic angle spinning (MAS) NMR and could be related..