Integral Membrane Proteins in Nanodiscs Can Be Studied by Solution NMR Spectroscopy

摘要

Investigation of large protein complexes with liquid-state NMR spectroscopy is limited by slow rotational diffusion of the particles. Increasing molecular mass translates into slower tumbling motions, causing rapid transverse relaxation of nuclear spins, broadening, and eventually disappearance of NMR signals. Transverse relaxation-optimized spectroscopy (TROSY) in combination with protein deuteration and improved hardware has pushed the virtual mass limit of solution NMR above 100 kDa for single water-soluble proteins. Individual components of macromolecular complexes as big as 900 kDa have been studied with TROSY-based NMR. However, integral membrane proteins (IMPs) in cellular membranes or liposomes constitute even larger particles and remain out of reach for solution NMR.