Abstract
In the last two decades, a wealth of structural and functional knowledge has been obtained for the three major cytoskeletal motor proteins, myosin, kinesin and dynein, which we review here. The cytoskeletal motor proteins myosin and kinesin are structurally similar in the core architecture of their motor domains and have similar force-producing mechanisms that are coupled with the chemical cycles of ATP binding, hydrolysis, Pi release and subsequent ADP release. The force is generated through conformational changes in the motor domain during Pi release and ATP binding in myosin and kinesin, respectively, and then converted into the rotation of the lever arm or neck linker (referred to as a power stroke) through the common structural pathways. On the other hand, the dynein cytoskeletal motor is an AAA+ protein and has a different structure and power stroke mechanism from those of myosins and kinesins. The linker protruding from the AAA+ ring of dynein swings according to the ATPase states, which, presumably, generates force to carry cargos within a cell. The communication mechanism between the track-binding and ATPase domains of dynein is unique because the two helices that presumably slide with respect to each other work as coordinators for these domains. Details of the mechanism underlying the power stroke and interdomain communication were revealed through recent progress in the structural studies of myosin, kinesin and dynein.
Highlights
The first cytoskeletal motor, myosin, was discovered from muscle by Szent-Györgyi and colleagues in the early 1940s (Table 1) (Banga and Szent-Györgyi 1941–1942)
The overall structure of dynein is different from myosin and kinesin (Burgess et al 2003), which suggests that there is a difference in the mechanism of the power stroke
We demonstrated that flagellar dynein had a similar overall structure of the distal stalk region containing the microtubule-binding domain (MTBD) in aqueous solution (Kato et al 2014)
Summary
The first cytoskeletal motor, myosin, was discovered from muscle by Szent-Györgyi and colleagues in the early 1940s (Table 1) (Banga and Szent-Györgyi 1941–1942). Power stroke means the movement of the lever arm (myosin) or neck linker (kinesin) in the state bound to actin filament or microtubule The minimal unit for the motor activity of dynein contains the linker, six tandemly arranged AAA+ modules with various amino acid sequences, a stalk, a microtubule-binding domain (MTBD) and a C sequence (Fig. 4). Previous EM studies combined with protein engineering have inserted tags in various sites within the polypeptide chain of the motor unit of cytoplasmic dynein, which include studies that Arisaka contributed to, along with the Burgess group Their results revealed that swing motion by the lever-like linker occurs between AAA2 and the stalk base (Roberts et al 2009). It was proposed that tension is generated between the stalk and strut upon structural change of the AAA+ ring, which causes change in the registry and structure of the stalk, and causes the MTBD to change its affinity to microtubules
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