Determination of Solid-State NMR Structures of Proteins by Means of Three-Dimensional 15N−13C−13C Dipolar Correlation Spectroscopy and Chemical Shift Analysis

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Abstract
In this paper, a three-dimensional (3D) NMR-based approach for the determination of the fold of moderately sized proteins by solid-state magic-angle spinning (MAS) NMR is presented and applied to the α-spectrin SH3 domain. This methodology includes the measurement of multiple 13C−13C distance restraints on biosynthetically site-directed 13C-enriched samples, obtained by growing bacteria on [2-13C]glycerol and [1,3-13C]glycerol. 3D 15N−13C−13C dipolar correlation experiments were applied to resolve overlap of signals, in particular in the region where backbone carbon−carbon correlations of the Cα−Cα, CO−CO, Cα−CO, and CO−Cα type appear. Additional restraints for confining the structure were obtained from φ and ψ backbone torsion angles of 29 residues derived from Cα, Cβ, CO, NH, and Hα chemical shifts. Using both distance and angular restraints, a refined structure was calculated with a backbone root-mean-square deviation of 0.7 Å with respect to the average structure.