Phosphorylation of myosin light chain modulates the in vitro movement of fibrils composed of actin and myosin filaments from skeletal muscle

In vitro movement of fibrils composed of actin and myosin filaments purified from skeletal muscle was observed by dark field microscopy during superprecipitation at low ionic strengths at room temperature. The movement was activated by phosphorylation of light chain (LC2) of myosin. The activity of the movement was evaluated in terms of the spreading of the area where the fibrils were moving. Adenosine triphosphatase activity of actomyosin was also enhanced by phosphorylation of LC2 and was correlated with the activity of the in vitro movement.