Molecular Nanosystems for Elucidating the Principle of Muscle Contraction

Abstract

The sarcomere, the minimal mechanical unit of muscle, imposes a geometric restriction on myosin in force generation. However, how single myosins generate force within the restriction remains elusive. Here we engineered thick filaments using DNA origami that incorporate muscle myosin to directly visualize the motion of the heads during force generation in a restricted space. We found that when the head diffuses, it weakly interacts with actin filaments and then strongly binds preferentially to the forward region as a Brownian ratchet. Upon strong binding, the two-step reversible lever-arm swing occurred. Our results illustrate the usefulness of our DNA origami-based assay system to dissect the mechanistic details of motor proteins.