Myosins are typical
molecular motor proteins that convert the chemical energy from the
ATP hydrolysis into mechanical work. The fundamental mechanism of this energy conversion is still unknown. To explain the experimental results already obtained, Masuda has proposed a hypothesis called the "Driven by Detachment" theory for the working principle of the
myosins. This theory insists that the energy used during the power
stroke of the
myosins does not directly originate from the chemical energy of
ATP, but is converted from the elastic energy within the molecule at the joint between the head and neck domains. One method for demonstrating the validity of this theory is a computational simulation using the molecular dynamics (MD) method. The MD software used was GROMACS. The target of the MD simulations was
myosin subfragment-1 (S1), for which the initial structure was obtained from the
Protein Data Bank entry 1M8Q. The AFM pull code of GROMACS was used to apply an external force of 17 pN at the end of the neck domain in the direction opposite to the power
stroke to observe whether the
myosin S1 takes the pre-power
stroke conformation. The residues assumed to be engaged in the docking with an actin filament were fixed to the space. Starting from exactly the same initial position, 10 simulations were repeated by varying the random seeds for generating the initial velocities of the atoms. After 64ns of calculations, the
myosin S1 took the conformation of the pre-power
stroke state in which the neck domain was bent around the joint between the head and the neck domains. This result agrees with the prediction expected by the DbD theory, the validity of which may be established by conducting similar simulations for the other steps of the
myosin working processes.