Conformational changes in α- and β-tubulin monomers. (A, C, E, and G) Contour plots with statistical significance. Colorings of t maps are same as in Fig. 3 D. (B, D, F, and H) Rigid body fitting of the atomic model. Regions with large subdomain movements are shown (N2 domain of β-tubulin in B and D, N1 domain of α-tubulin in F and H, and I domain of α-tubulin in H). The gray and colored ribbons show atomic models before and after subdomain fitting, respectively. The α-tubulins are colored red (N domain) and cyan (I domain), whereas the β-tubulins are colored brown (N domain) and blue (I domain). Sectioning planes and orientations of the views for C–D, E–F, and G–H are shown in A (black boxes). The brown circle shows the tight bond at the intratubulin dimer junction. The star indicates the putative site for Lys-40 of α-tubulin. Bars, 2 nm.