Detergent-Free Isolation of Membrane Proteins and Strategies to Study Them in a Near-Native Membrane Environment

Abstract

Atomic-resolution structural studies of membrane-associated proteins and peptides in a membrane environment are important to fully understand their biological function and the roles played by them in the pathology of many diseases. However, the complexity of the cell membrane has severely limited the application of commonly used biophysical and biochemical techniques. Recent advancements in NMR spectroscopy and cryoEM approaches and the development of novel membrane mimetics have overcome some of the major challenges in this area. For example, the development of a variety of lipid-nanodiscs has enabled stable reconstitution and structural and functional studies of membrane proteins. In particular, the ability of synthetic amphipathic polymers to isolate membrane proteins directly from the cell membrane, along with the associated membrane components such as lipids, without the use of a detergent, has opened new avenues to study the structure and function of membrane proteins using a variety of biophysical and biological approaches. This review article is focused on covering the various polymers and approaches developed and their applications for the functional reconstitution and structural investigation of membrane proteins. The unique advantages and limitations of the use of synthetic polymers are also discussed.

Polymer-Nanodiscs as a Novel Alignment Medium for High-Resolution NMR-Based Structural Studies of Nucleic Acids

“…With their long-term stability, as indicated by deuterium NMR, the polymer-nanodiscs can be used to record multi-dimensional biomolecular NMR experiments that require longer-acquisition times. Furthermore, due to lipid-solubilizing properties, SMA-EA can be used to directly isolate membrane proteins along with native lipids [ 61 , 69 ], and its compatibility with divalent metal ions makes it suitable for studying metalloproteins and metal-bound nucleic acids. Thus, the polymer-nanodiscs are excellent tools for studying the conformation of membrane proteins, soluble proteins, and nucleic acids (current study) and can even extend to characterize natural products and small-molecule drug candidates in drug-development studies [ 70 , 71 , 72 , 73 ].…”

Application of synthetic lipid droplets in metabolic diseases

“…The application of this technique to synthetic LDs would allow researchers to more precisely mimic subcellular compartments and better resolve the dynamic function of LDs in the cell. 88…”

“…Such nanoparticles, which are called nanodiscs, are excellent membrane mimetics and are used for various applications. The application of this technique to synthetic LDs would allow researchers to more precisely mimic subcellular compartments and better resolve the dynamic function of LDs in the cell 88 …”

Fabrication of membrane proteins in the form of native cell membrane nanoparticles using novel membrane active polymers

“…Conversely, the stability of nanodiscs has been established to be contingent upon lipid composition. 42,43 Thus, our study delved into the potential inuence of polymeric side chains on lipid selectivity. This was achieved by analyzing the extracted lipid composition using mass spectrometry (MS) techniques.…”