Biomolecular solid-state nuclear magnetic resonance methods for spectral assignment and high-resolution structure determination of proteins

Multidimensional solid-state nuclear magnetic resonance (SSNMR) experiments for the elucidation of structure in microcrystalline proteins are presented, utilizing the streptococcal beta-1 immunoglobulin binding domain of protein G (GB1) as a model protein. Complete 13C and 15N chemical shifts are presented based on 2D 13C-13C, 15N-13C and 3D 15N-13C- 13C and 13C-15N-13C correlation spectra. Aromatic signal assignments are performed with customized experiments and processing schemes. Dynamics are analyzed qualitatively, accounting for variations in cross-peak intensities. Dipolar-shift spectra quantify dynamics along the backbone. 4D 13C-15N-13C- 13C experiments are developed to enhance spectral resolution and ease assignment. G-Matrix Fourier transform experiments are applied to solid protein samples which reduce the acquisition time of high dimensional experiments. New types of structural restraints for solid proteins are acquired and analyzed by an iterative assignment method. Three dimensional experiments determine multiple CH-NH and NH-NH relative dipole tensor orientations, utilized as highly accurate restraints. Simulated annealing protocols are optimized for SSNMR data, treating distance restraints semi-empirically and applying precise vector angle restraints. These efforts result in the highest resolution (0.31 A backbone RMSD) protein structure so far determined by SSNMR.