Fig. 2: Structural characterization of the DISC1 C-region using a combination of NMR spectroscopy and EM.

In all spectra displayed in the figures, the protein was uniformly ¹³C- and ¹⁵N-labeled. A 2D (¹H–¹⁵N)-HSQC spectra of the C-region in solution (red) and solid state (black) at a MAS rate of 30 kHz. Green diamonds represent solution NMR CS of the truncated version of the DISC1 C-region (PDB ID 5YIH) and black annotations are likely assignments of C-region resonances based on proximity to the solution NMR signals. B 2D PDSD (red) and INEPT-TOBSY (black) ¹³C–¹³C spectra, diamond-shaped marks in yellow, blue, and green represent average CS (ref. [47]) of residues in helices, coiled regions (RC), and strands, respectively. The box depicts the region where the presence of β-strand-specific CS is expected in dipolar coupling-based experiments for residues such as Ala, Leu, and Ser. C Negatively stained EM image of the DISC1 C-region showing the presence of fibrillar protein along with oligomers. D 2D class averages of the tetramer and the fibril. For better visualization of the overall fibrillar structure, one class (top) was calculated by ignoring the CTF until the first peak. The 3D reconstructions of the tetramer and the fibril are displayed as surface representations alongside the best-fitting structural model docked within the density map (also see Figs. 4 and S8).