The molecular basis of DCX selective stabilization of B-lattice 13-pf MTs. (A) Front view and schematic of the 8.2 Å resolution cryo-EM map of DCX–MTs fitted with structures of α-tubulin and β-tubulin (map, violet surface; 1JFF.pdb, α in blue, β in cyan ribbons; Löwe et al., 2001) and the solution structure of the N-DC domain of DCX (map, yellow surface; 1MJD.pdb, model 11, residues 46–140, orange; Kim et al., 2003). See also Fig. S2 and Video 1. The four dimers forming the DCX binding site are labeled αβ_1–4. Tubulin helices α₁-H10, α₂-H4,H12, β₃-H3,H11,H12, and tubulin strand α₂-S7 are labeled, as are the aa numbers of the boundaries of N-DC and α₁ and β₄ C termini. (B) View from inside toward the outside of the MT, illustrating the quality of the fit of N-DC in the density. (C) Front view of tubulin aa <5 Å away from DCX displayed as a molecular surface colored by heteroatom in which four major binding patches can be identified. (D) Sections of a sequence alignment of the main isoforms of bovine tubulin used in our structure (1JFF-A and 1JFF-B), and of other human tubulin isoforms (TUBA1A, GenBank/EMBL/DDBJ accession no. 7846; TUBA3D, accession no. 113457; TUBB2B, accession no. 347733; TUBB3, accession no. 10381). DCX contacts are boxed in red. α-tubulins are highlighted in blue and β-tubulins in cyan; sequence identities are highlighted in black; secondary structures of 1JFF-A are depicted below. (E and F) Location of side chains of surface residues whose mutations cause neuronal migration disorders: S47R, Y64N, R76S, R78H/L, D86H, R89G, R102S in N-DC of DCX (orange text); P263T and R264C in TUBA1A, a human α-tubulin isoform (blue text).