Journal or Book Title
The dynamic and structural properties of membrane proteins are intimately affected by the lipid bilayer. One property of membrane proteins is uniaxial rotational diffusion, which depends on the membrane viscosity and thickness. This rotational diffusion is readily manifested in solid-state NMR spectra as characteristic line shapes and temperature-dependent line narrowing or broadening. We show here that this whole-body uniaxial diffusion is suppressed in lipid bilayers mimicking the composition of eukaryotic cell membranes, which are rich in cholesterol and sphingomyelin. We demonstrate this membrane-induced immobilization on the transmembrane peptide of the influenza A M2 (AM2-TM) proton channel protein. At physiological temperature, AM2-TM undergoes uniaxial diffusion faster than ∼105 s−1 in DLPC, DMPC, and POPC bilayers, but the motion is slowed by 2 orders of magnitude, to <103 s−1, in a cholesterol-rich virus envelope−mimetic membrane (“viral membrane”). The immobilization is manifested as near rigid-limit 2H quadrupolar couplings and 13C−1H, 15N−1H, and 13C−15N dipolar couplings for all labeled residues. The immobilization suppresses intermediate time scale broadening of the NMR spectra, thus allowing high-sensitivity and high-resolution spectra to be measured at physiological temperature. The conformation of the protein in the viral membrane is more homogeneous than in model PC membranes, as evidenced by the narrow 15N lines. The immobilization of the M2 helical bundle by the membrane composition change indicates the importance of studying membrane proteins in environments as native as possible. It also suggests that eukaryote−mimetic lipid membranes may greatly facilitate structure determination of membrane proteins by solid-state NMR.
American Chemical Society
Luo, Wenbin; Cady, Sarah D.; and Hong, Mei, "Immobilization of the Influenza A M2 Transmembrane Peptide in Virus Envelope−Mimetic Lipid Membranes: A Solid-State NMR Investigation" (2009). Chemistry Publications. 1148.