Solid-state magic-angle spinning NMR of outer-membrane protein G from Escherichia coli

Uniformly C-13, N-15-labelled outer-membrane protein G (OmpG) from Escherichia coli was expressed for structural studies by solid-state magic angle spinning (MAS) NMR. Inclusion bodies of the recombinant, labelled protein were purified under denaturing conditions and refolded in detergent. OmpG was reconstituted into lipid bilayers and several milligrams of two-dimensional crystals were obtained. Solid-state MAS NMR spectra showed signals with an apparent line width of 80-120 Hz (including homonuclear scalar couplings). Signal patterns for several amino acids, including threonines, prolines and serines were resolved and identified in 2D proton-driven spin-diffusion (PDSD) spectra.