Investigating the Structural and Dynamic Properties of Membrane Proteins with Solid-State NMR, CW-EPR, ESEEM, and DEER Spectroscopic Techniques

Abstract

Currently, we have very limited structural and dynamic information on membrane proteins and peptides. New spectroscopic methods are needed to probe these systems in a lipid bilayer. In order to address these issues, the Lorigan lab developing unique hybrid solid-state NMR and spin-label EPR spectroscopic techniques. Magnetic resonance spectroscopic data of 15N-, g2H-labeled and/or spin-labeled membrane proteins incorporated into vesicles and bicelles will be presented. State-of-the-art solid-state NMR and pulsed EPR techniques such as Magic Angle Spinning (MAS) NMR, Electron Spin Echo Envelope Modulation (ESEEM) spectroscopy, and Double Electron-Electron Resonance (DEER) spectroscopy will be used. The ESEEM technique can determine short to medium range distances (out to about 8 Å) between a site-specific nitroxide spin label (MTSL) and a nearby NMR-active isotopic labeled residue for a variety of different peptides and proteins which ultimately can be used to determine the difference between an α-helical and β-sheet secondary structure. DEER can be used to measure distances between 2 spin labels out to about 70 Å. The advantages and disadvantages of applying solid-state NMR and EPR spectroscopy to probe the structural and dynamic properties of membrane proteins will be discussed.