Nuclear Magnetic Resonance ( NMR ) of Proteins: Solid State

Abstract

Solid‐state nuclear magnetic resonance (NMR) spectroscopy is a powerful technique for examining the structures of protein assemblies and complexes that are unsuitable for analysis by diffraction methods. Structural details are obtained for challenging systems including membrane proteins in lipid bilayers and water‐insoluble fibrillar proteins. High‐resolution spectra of proteins in solid or gel phases lacking long‐range order are obtained with magic‐angle spinning and, for membrane‐embedded proteins, further anisotropic information is gained from spectra of stationary, macroscopically aligned samples. The information obtained defines the secondary structure and global fold of the protein, and also the orientation and topology of membrane proteins within lipid bilayers. These methods have elucidated, amongst other things, the structures of ion channels and their interactions with antiviral drugs and toxins and the molecular architectures of amyloid fibrils associated with Alzheimer's disease and type II diabetes. In addition, the molecular conformations of numerous ligands have been determined in the sites of action within their biological receptor proteins. Key Concepts: For solid‐state NMR measurements on biological materials, samples are either macroscopically aligned or are rotated at the magic‐angle. Solid‐state NMR measurements on aligned membrane proteins provide anisotropic restraints on the orientations of contiguous peptide planes or domains relative to the lipid bilayer. Magic‐angle spinning provides high‐resolution spectra containing information on isotropic chemical shifts and interatomic distances and torsional angles. Both approaches require isotopic labelling ( 13 C and 15 N supplemented as necessary with deuteration) of the protein.