Structure Determination of Membrane Peptides and Proteins by Solid-State NMR

Abstract

Solid-state nuclear magnetic resonance (NMR) spectroscopy provides useful information on the structure, topology, and orientation of peptides and proteins bound to lipid bilayers. The structure and orientation of membrane-associated peptides and proteins can be elucidated by analyzing structural constraints obtained from anisotropic chemical-shift interactions, nuclear dipolar interactions, or a combination of these interactions. Detailed structures of various peptides and proteins in their membrane-bound states can be studied by analyzing anisotropic chemical-shift interactions by, for example, chemical-shift oscillation analysis, and nuclear dipolar interactions using techniques such as polarity index slant angle wheel analysis. Magic-angle spinning (MAS) experiments coupled with cross-polarization (CP) and high-power decoupling (CP-MAS) techniques provide high-resolution 13C and 15N NMR signals for selectively or uniformly labeled membrane-bound peptides and proteins in solid-state NMR. Furthermore, homonuclear and heteronuclear dipolar interactions can be recoupled using various spin manipulation pulse sequences under MAS conditions. These experiments enable the correlation of 13C–13C and 13C–15N signals, allowing their assignment to specific amino acid residues and ultimately determination of the high-resolution structure of membrane-bound peptides and proteins.