Structural and dynamic studies of the γ-M4 trans-membrane domain of the nicotinic acetylcholine receptor

A structural characterization of a synthetic peptide corresponding to the fourth transmembrane domain (M4-TMD) of the gamma-subunit of the nicotinic acetylcholine receptor from Torpedo californica has been undertaken. Solid-state NMR and CD spectroscopy studies indicate that upon reconstitution into lipid vesicles or magnetically aligned lipid bilayers, the synthetic M4-TMD adopts a linear alpha-helical conformation with the helix aligned within 15 degrees of the membrane normal. Furthermore, analysis of the motional averaging of anisotropic interactions present in the solid-state NMR spectra of the reconstituted peptide, indicate that the dynamics of the peptide within the bilayer are highly sensitive to the phase adopted by the lipid bilayer, providing an insight into how the interaction of lipids with this domain may play a important role in the modulation of this receptor by its lipid environment.

Manipulation of the director in bicellar mesophases by sample spinning: a new tool for NMR spectroscopy

It is shown that bicellar nematic liquid-crystalline phases can be oriented with the director (the normal to the bicellar plane) at an arbitrary angle to the applied magnetic field by sample rotation around one axis (variable-angle sample spinning) or around two axes successively (switched-angle spinning). This promises to open novel possibilities for NMR studies of bicelles and proteins incorporated into bicelles or dissolved in a solution containing bicelles, including the correlation of several orientations in a two-dimensional NMR experiment.