Extended Data Fig. 4: Double-spiral fold of TDP-43 filaments from ALS with FTLD.

a, Schematic view of the double-spiral fold. The two hydrophobic clusters in the hydrophobic nucleus, composed of the side chains of M307, M311, F313, M322, M323, A326, A329 and L330 (cluster 1); and A328, W334, M336 and L340 (cluster 2), are numbered. b, Hydrophobicity of the double-spiral fold from most hydrophilic (cyan) to most hydrophobic (yellow). c, Secondary structure of the double-spiral fold, depicted as five successive rungs. The glycine-rich (G282-G310, magenta), hydrophobic (M311-S342, white) and Q/N-rich (Q343-Q360, green) regions are highlighted. d, Views of the double-spiral fold, depicted as three successive rungs, showing hydrogen bonds (blue dashed lines) between buried polar side chains and main chain peptide groups. e, Superposition of residues N319-A326 of the double-spiral fold (cyan), depicted as two successive rungs, with residues G88-M95 and G107-A114 of the β-helix domain of glutamate synthase (magenta, PDB ID 1EA0). f, Unmasked cryo-EM 3D reconstructions of TDP-43 filaments from the frontal and motor cortices of individual 1 and from the frontal cortex of individual 2, shown as central slices perpendicular to the helical axis. Additional density within the prominent groove on the filament surface formed by the main chain of G282–Q286 and the side chain of Q286 is indicated with a magenta arrow. Additional densities adjacent to flat strips on the surface of the glycine-rich spiral branch between R293 and A315 are indicated with yellow arrows. Additional less well-resolved density projecting from a polar patch formed by the side chains of N352, Q354 and Q356 on the surface of the Q/N-rich spiral branch is indicated with a cyan arrow. Scale bars, 25 Å.