Structures and Dynamics of Native-State Transmembrane Protein Targets and Bound Lipids

Abstract

Membrane proteins work within asymmetric bilayers of lipid molecules that are critical for their biological structures, dynamics and interactions. These properties are lost when detergents dislodge lipids, ligands and subunits, but are maintained in native nanodiscs formed using styrene maleic acid (SMA) and diisobutylene maleic acid (DIBMA) copolymers. These amphipathic polymers allow extraction of multicomponent complexes of post-translationally modified membrane-bound proteins directly from organ homogenates or membranes from diverse types of cells and organelles. Here, we review the structures and mechanisms of transmembrane targets and their interactions with lipids including phosphoinositides (PIs), as resolved using nanodisc systems and methods including cryo-electron microscopy (cryo-EM) and X-ray diffraction (XRD). We focus on therapeutic targets including several G protein-coupled receptors (GPCRs), as well as ion channels and transporters that are driving the development of next-generation native nanodiscs. The design of new synthetic polymers and complementary biophysical tools bodes well for the future of drug discovery and structural biology of native membrane:protein assemblies (memteins).

Mechanisms of Formation, Structure, and Dynamics of Lipoprotein Discs Stabilized by Amphiphilic Copolymers: A Comprehensive Review

“…Early experiments conducted in the late 1990s–early 2000s suggested a copolymer of styrene and maleic anhydride (SMA) as one of the first amphiphilic agents for direct and efficient solubilization of membrane peptides or proteins [ 11 ], which was later extensively optimized and since then became extremely widespread for biophysical and structural characterization of MPs [ 12 , 13 , 14 ].…”

Endothelial Cell Plasma Membrane Biomechanics Mediates Effects of Pro-Inflammatory Factors on Endothelial Mechanosensors: Vicious Circle Formation in Atherogenic Inflammation

“…The "force-from-lipid" model suggests the gating of mechanosensitive ion channels with inputs from the lipid bilayer, while the "force-from-filament" model suggests primary roles of the extracellular matrix and intracellular cytoskeleton (CSK) in the mechanical activation of ion channels [32]. Great efforts have been devoted to deciphering the multi-ple effects exerted by membrane lipids on the structure and function of transmembrane proteins [33][34][35][36][37][38][39][40][41][42][43][44].…”

Synthesis and Evaluation of a Library of Alternating Amphipathic Copolymers to Solubilize and Study Membrane Proteins

“…[4][5][6][7] This preservation of the endogenous lipidic environment confers high stability to the MPs, and allows for the study of (native) lipid-protein and protein-protein interactions. [7][8][9][10][11] The MPs in the nanodiscs furthermore are amenable to functional and structural studies with an array of biophysical techniques, 12 including mass spectrometry, 13 mass photometry, 14 NMR spectroscopy, 15,16 and cryo-electron microscopy. 5,17,18 The efficiency of membrane solubilization by SMA copolymers is determined by many factors, including environmental conditions such as ionic strength and pH, 19,20 physicochemical properties of the target membrane [21][22][23] and properties of SMA, such as length and chemical composition.…”