First Dynein Protein Structure Reported

The motor protein dynein, which carries molecular cargo along microtubule tracks in cells, is less understood than other motor proteins such as kinesin and myosin. Dynein's motor region consists of a microtubule-binding domain, an ATPase domain that hydrolyzes adenosine triphosphate, and a 15-nm coiled-coil stalk connecting them. Ronald D. Vale of the University of California, San Francisco; Ian R. Gibbons of UC Berkeley; Ronald A. Milligan of Scripps Research Institute; and coworkers report the first atomic-resolution structure of any part of dynein—the microtubule-binding domain and part of the stalk—as well as a cryo-electron microscopy map of the microtubule-binding domain bound to a microtubule (Science 2008, 322, 1691). The structure supports a previous proposal that sliding motions between two helices in the stalk serve as a communication mechanism between the microtubule-binding domain and the ATPase domain. In functional studies, when the researchers flipped the orientation of the ATPase domain relative to the microtubule-binding domain by 180° dynein continued to move in the same direction along the microtubule. This result suggests that the microtubule-binding domain, rather than the ATPase domain, dictates the direction in which dynein travels.