  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 structural
change, we propose a "dual Go-model," a variant of the Go-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.
