Fig. 2.

Actin structural changes in cofilactin. a Comparison between the G-actin (1J6Z, magenta, G-form) and actin subunit in cofilactin (green, C-form). The actin molecule is considered to have two domains, the inner domain (ID, blue ellipse) and outer domain (OD, red ellipse). Each domain is divided into two subdomains, OD into subdomains 1 and 2, and ID into 3 and 4. Each subdomain is indicated by a number (1, 2, 3 and 4). The structures are aligned through superimposition of the IDs. b Side view of a, rotated by 90°. Green and magenta arrows represent the orientation of two α-helices (79–95, 359–365) of the C-form and G-form, respectively. The two α-helices shift but do not tilt in the structural change. c Comparison between the G-form and F-form (5JLF, cyan). The structures are aligned through superimposition of the IDs. d Side view of c. Blue and magenta arrows represent the orientation of the two α-helices (79–95, 359–365) of the F-form and G-form, respectively. The two α-helices tilt in the structural change²³. e Rotation axes. G/F axis (red) and G/C axis (orange) are superposed on the G-form (1J6Z, magenta). f Top view of e. g The G-form (1J6Z, magenta), F-form (5JLF, cyan) and C-form (green) are superposed by aligning the rigid bodies of the ID (blue in Fig. 2i). h The three forms are superposed by aligning the rigid bodies of SD1 (red in Fig. 2i) as in G. i Rigid bodies in the ID and SD1 are shown in blue and red, respectively