Saponins Form Nonionic Lipid Nanodiscs for Protein Structural Studies by Nuclear Magnetic Resonance Spectroscopy
Year: 2022
Type: article
Abstract: Structural studies of membrane proteins in native-like environments require the development of diverse membrane mimetics. Currently there is a need for nanodiscs formed with nonionic belt molecules to avoid nonphysiological electrostatic interactions between the membrane system and protein of interest. Here, we describe the formation of lipid nanodiscs from the phospholipid DMPC and a class of nonionic glycoside natural products called saponins. The morphology, surface characteristics, and magnetic alignment properties of the saponin nanodiscs were characterized by light scattering and solid-state NMR experiments. We determined that preparing nanodiscs with high saponin/lipid ratios reduced their size, diminished their ability to spontaneously align in a magnetic field, and favored insertion of individual saponin molecules in the lipid bilayer surface. Further, purification of saponin nanodiscs allowed flipping of the orientation of aligned nanodiscs by 90°. Finally, we found that aligned saponin nanodiscs provide a sufficient alignment medium to allow the measurement of residual dipolar couplings (RDCs) in aqueous cytochrome c.
Authors: Samuel D. McCalpin, Thirupathi Ravula, Ayyalusamy Ramamoorthy
Institution: University of Michigan
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W4213097463