Solid State NMR Strategy for Characterizing Native Membrane Protein Structures

Abstract

Unlike water soluble proteins, the structures of helicaltransmembrane proteins depend on a very complex environment. These proteins sit in the midst of dramatic electrical and chemical gradients and are often subject to variations in the lateral pressure profile, order parameters, dielectric constant, and other properties. Solid state NMR is a collection of tools that can characterize high resolution membrane protein structure in this environment. Indeed, prior work has shown that this complex environment significantly influences transmembrane protein structure. Therefore, it is important to characterize such structures under conditions that closely resemble its native environment. Researchers have used two approaches to gain protein structural restraints via solid state NMR spectroscopy. The more traditional approach uses magic angle sample spinning to generate isotropic chemical shifts, much like solution NMR. As with solution NMR, researchers can analyze the backbone chemical shifts to obtain torsional restraints. They can also examine nuclear spin interactions between nearby atoms to obtain distances between atomic sites. Unfortunately, for membrane proteins in lipid preparations, the spectral resolution is not adequate to obtain complete resonance assignments. Researchers have developed another approach for gaining structural restraints from membrane proteins: the use of uniformly oriented lipid bilayers, which provides a method for obtaining high resolution orientational restraints. When the bilayers are aligned with respect to the magnetic field of the NMR spectrometer, researchers can obtain orientational restraints in which atomic sites in the protein are restrained relative to the alignment axis. However, this approach does not allow researchers to determine the relative packing between helices. By combining the two approaches, we can take advantage of the information acquired from each technique to minimize the challenges and maximize the quality of the structural results. By combining the distance, torsional, and orientational restraints, we can characterize high resolution membrane protein structure in native-like lipid bilayer environments.

Ultra fast magic angle spinning solid – state NMR spectroscopy of intact bone

“…[14,15] Hitherto, ssNMR has become a robust and imminent tool to study biomaterials such as bone. [16][17][18][19][20][21][22][23][24] ssNMR can be exclusively implemented to study all the three major components of bone, organic part, [25][26][27] inorganic part [28][29][30][31] and water.…”

Biosilica and bioinspired silica studied by solid-state NMR

“…[1] Solid state NMR (SSNMR) has seen an impressive development in the last years, thanks to the development of higher field instruments, higher spinning speeds, improved pulse sequences and sample preparation methods. This allowed for the exploration of a large number of systems that can be studied at atomic resolution only by SSNMR such as fibrils, [2][3][4] membrane proteins [4][5][6][7] and large protein aggregates [8][9][10][11].…”

Isotope Labeling of Eukaryotic Membrane Proteins in Yeast for Solid-State NMR

“…Besides the main technical challenges related to functional expression, stability in detergents, and crystallization, X-ray crystallography and solution NMR often face a conceptual problem of providing a native-like environment for membrane proteins, being restricted to using three-dimensional protein crystals or small detergent micelles. In this respect, an emerging powerful technique of solid-state NMR (ssNMR) provides an attractive alternative, as it allows studies of membrane proteins in the artificial native-like lipid bilayers or even in the native membranes, without having any inherent limitations on the protein molecular weight (Hong, Zhang, & Hu, 2012;Judge, Taylor, Dannatt, & Watts, 2015;Murray, Das, & Cross, 2013;Opella, 2015;Renault et al, 2012;Wang & Ladizhansky, 2014;Ward, Brown, & Ladizhansky, 2015). In the last few years, several structures of polytopic membrane proteins and their oligomers have been determined by ssNMR (Das et al, 2015;Park et al, 2012;Shahid et al, 2012;Wang et al, 2013), making it a reputable player in the team of structural biology techniques.…”