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Structural Change and Nucleotide Dissociation of Myosin Motor Domain: Dual G Model Simulation

Fumiko Takagi ^*  and Macoto Kikuchi  ^*

^* Formation of Soft Nanomachines, Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Osaka, Japan; and Cybermedia Center Osaka University, Osaka, Japan

Correspondence: Address reprint requests to F. Takagi, E-mail: fumiko{at}cp.cmc.osaka-u.ac.jp.

We investigated the structural relaxation of myosin motor domain from the pre-power stroke state to the near-rigor state using molecular dynamics simulation of a coarse-grained protein model. To describe the spontaneous structural change, we propose a dual G-model—a variant of the G-like model that has two reference structures. The nucleotide dissociation process is also studied by introducing a coarse-grained nucleotide in the simulation. We found that the myosin structural relaxation toward the near-rigor conformation cannot be completed before the nucleotide dissociation. Moreover, the relaxation and the dissociation occurred cooperatively when the nucleotide was tightly bound to the myosin head. The result suggested that the primary role of the nucleotide is to suppress the structural relaxation.