Sections of the density map of the wild type. (a–e) Vertical sections (perpendicular to the microtubule) of the wild-type flagellum. AAA rings of the heavy chains of inner and outer dynein arms are marked by green lines. The solid lines show the sections of the planes of the rings. Corresponding locations and the orientations of the inner arm dynein rings are shown in the longitudinal section (f; so the lines in a–e and the lines in f are perpendicular to each other). (a) The section including dynein fβ. (b) Dynein fα. The distance from a is 75 Å. (c) Dynein a or d (180 Å from a). (d) Dynein c (450 Å from a). (e) Dynein e (580 Å). Dotted lines are extensions in the same plane as the rings and are presumed to represent the orientation of the stalks. ODA, outer dynein arm. Bar, 20 nm.