cytoplasmic dynein, microtubule binding site
house mouse (Mus musculus), thermophile (Thermus thermophilus)
Dynein is a motor protein, moving along microtubules, which are cytoskeleton, to their minus end-direction, with hydrolyzing ATP. There are two kinds of dynein molecules: axonemal dynein and cytoplasmic dynein. The former axonemal dynein works as the force-generating motors of flagella and cilia. In contrast, the latter cytoplasmic dynein shown here is involved in several cellular processes, such as transform of cellular vesicles and organella and regulation of mitotic checkpoint.
Cytoplasmic dynein works as a dimer, and it "walks" on the microtubules to produce power by binding and unbinding to the microtubules, synchronizing with the reaction cycle of the ATP hydrolysis. Dynein is categorized as the AAA+ ATPase, and it is mainly composed of the three structural domains: a AAA+ ring domain with the six AAA+ modules, a rod-like "stem" domain, and a "stalk" that includes the microtubule-binding domain.
The ATPase activity is located in the 1st to the 4th AAA+ module of the motor domain. The stem is involved in dimerization of the heavy chain of dynein and in complex formation with the intermediate and light chains, and the stalk is associated with microtubule binding. In the dynein structure, those two domains extend from the AAA+ ring domain. Here shows the microtubule-binding domain, which is a globular domain located at the tip of the long stalk that extends from the AAA+ ring domain. The 15 nm stalk consists of flexible anti-parallel coiled-coil, and it separates the motor domain from the microtubule-binding domain. Structural change in the AAA+ ring domain with the ATP hydrolysis must transfer to the microtubule-binding domain through the stalk, and the structural change of the microtubule-binding domain should make binding and unbinding to the microtubules. Thus, the dynein dimer is considered to "walk" along the microtubules.
The structure shown here is a fusion protein of Ser-tRNA synthetase with the microtubule-binding domain of cytoplasmic dynein from mouse. From the affinity experiment, this structure is known to correspond to the weak-binding state, where the microtubule separates from the microtubule-binding domain.
Protein Data Bank (PDB)
Author: Yosuke Nishikawa Translator: Genji Kurisu and Haruki Nakamura