Uniaxial Diffusional Narrowing of NMR Lineshapes for Membrane Proteins Reconstituted in Magnetically Aligned Bicelles and Macrodiscs


Cite item

Full Text

Open Access Open Access
Restricted Access Access granted
Restricted Access Subscription Access

Abstract

Structure and dynamics of membrane proteins can be effectively studied by oriented-sample solid-state nuclear magnetic resonance (NMR) techniques when the lipid bilayers are macroscopically aligned with respect to the main magnetic field. Magnetic alignment of the protein-containing membrane bilayer results from the negative susceptibility anisotropy of the lipid hydrocarbon interior yielding perpendicular sample alignment. At this orientation, while the uniformity of alignment represents an essential prerequisite for obtaining high-quality NMR spectra, further line narrowing is obtained by uniaxial motional averaging of the azimuthal parts of the chemical shift anisotropies and dipolar couplings. The motional averaging is brought about by uniaxial rotational diffusion of the protein molecules about the normal to the membrane surface, which is perpendicular to the magnetic field. Uniaxial averaging is efficient when the motion about the axis of alignment becomes sufficiently fast (on the timescale of the dipolar couplings and chemical shift anisotropies). Line narrowing under uniaxial rotation can be theoretically modeled using the stochastic Liouville equation. In this mini-review, we illustrate the method of uniaxial averaging for the relatively small Pf1 coat protein which exhibits excellent resolution in magnetically aligned bicelles due to its fast uniaxial diffusion and even superior resolution in large (30 nm) nanodiscs (macrodiscs) stabilized by a belt peptide. Spectra of Pf1 coat protein in polymer-stabilized macrodiscs, an alternative and more robust alignment media, are presented. We also report on preliminary spectra of a much larger protein—uniformly 15N labeled M1-M4 domain for the human acetylcholine receptor. While some spectral resolution is apparent, significantly broader linewidths emphasize the need for creating fast rotating discoidal membrane mimetics.

About the authors

Deanna M. Tesch

Department of Chemistry, North Carolina State University; Department of Chemistry, Shaw University

Email: alex_nevzorov@ncsu.edu
United States, 2620 Yarbrough Drive, Raleigh, NC, 27695-8204; 118 E South St, Raleigh, NC, 27601

Zhaleh Pourmoazzen

Department of Chemistry, North Carolina State University

Email: alex_nevzorov@ncsu.edu
United States, 2620 Yarbrough Drive, Raleigh, NC, 27695-8204

Emmanuel O. Awosanya

Department of Chemistry, North Carolina State University

Email: alex_nevzorov@ncsu.edu
United States, 2620 Yarbrough Drive, Raleigh, NC, 27695-8204

Alexander A. Nevzorov

Department of Chemistry, North Carolina State University

Author for correspondence.
Email: alex_nevzorov@ncsu.edu
United States, 2620 Yarbrough Drive, Raleigh, NC, 27695-8204

Supplementary files

Supplementary Files
Action
1. JATS XML

Copyright (c) 2018 Springer-Verlag GmbH Austria, part of Springer Nature