Complete resolution of the solid-state NMR spectrum of a uniformly 15 N-labeled membrane protein in phospholipid bilayers

Abstract

Complete resolution of the amide resonances in a three-dimensional solid-state NMR correlation spectrum of a uniformly ¹⁵N-labeled membrane protein in oriented phospholipid bilayers is demonstrated. The three orientationally dependent frequencies, ¹H chemical shift, ¹H–¹⁵N dipolar coupling, and ¹⁵N chemical shift, associated with each amide resonance are responsible for resolution among resonances and provide sufficient angular restrictions for protein structure determination. Because the protein is completely immobilized by the phospholipids on the relevant NMR time scales (10 kHz), the linewidths will not degrade in the spectra of larger proteins. Therefore, these results demonstrate that solid-state NMR experiments can overcome the correlation time problem and extend the range of proteins that can have their structures determined by NMR spectroscopy to include uniformly ¹⁵N-labeled membrane proteins in phospholipid bilayers.