Fig. 1.

Sketch of the components of a single dynein head bound to a MT. The different AAA domains are shown as numbered spheres (1–6). The non-AAA C terminus domain (C) also is shown. ATP hydrolysis occurs primarily at AAA1. The dynein power stroke taking place in response to ADP release from AAA1 occurs in the direction shown by the thick curved arrow. AAA domains 2, 3, and 4 are proposed to play a regulatory role in force transmission through load-induced binding of nucleotides that can reduce the dynein step size (18).