Structure of the MTBD–MT complex. (A) CryoEM image of a 15-pf MT decorated with the high-affinity MTBD. Bar, 25 nm. (B) Three-dimensional image reconstruction of the MTBD–MT complex. The open square surrounding the MTBD-decorated MT density represents the plane of a slice through the volume, shown in C. (C) The top half of the density is shown in B, cut out at the plane and viewed from the minus end of the MT. (D and E) Fitting of the x-ray crystal structure of MTBD (PDB ID: 3VKH; Kon et al., 2012) into the map, viewed from the side of the MT with its minus end on the left (D) and right (E) sides. See Fig. S5 for the details of the modeling procedure. (F) Magnified view of the boxed area in D. Positively and negatively charged residues are shown in CPK representation with nitrogen atoms in blue and oxygen atoms in red. The putative position of CC1, inferred from the model of the MTBD of mouse cytoplasmic dynein (PDB ID: 3J1T; Redwine et al., 2012), is indicated by a thin helix. The color coding scheme for the MTBD helices used in D–F is that used by Carter et al. (2008). (G) Superposition of the crystal structure of the MTBD (PDB ID: 3VKH; white) and the model of the MTBD in the MTBD–MT complex (yellow). The structures of the MTBD spanning H2-CC2 (T3399-E3489) were superposed using the MatchMaker tool of UCSF Chimera (Meng et al., 2006).