Internal Lever Arm Model for Myosin II

Motor proteins are special enzymes capable of transforming chemical energy into mechanical work. One of the best known motor proteins belongs to the family of myosins found in eukaryotic tissues. The most studied - and first discovered type - of myosin is the skeletal muscle myosin (myosin II) which is the motor protein responsible for the contraction of muscle tissue. In the present study we propose an overdamped visco-elastic rigid body model, linked with springs, for myosin II, where an internal lever arm is added to the previously investigated lever arm model. Our model is based on the significant difference of two springs' stiffness, which is responsible for the sequence of steps of the motion (binding to actin vs. lever arm swinging). The model provides exponential time displacement curves which are consistent with experimental measurements.