Bidirectional movement of actin filaments along tracks of heavy meromyosin and native thick filaments.

Flexibility of the myosin molecule was studied by an in vitro motility assay in terms of the direction of actin movement. Actin filaments can move in both directions on tracks of heavy meromyosin made on a nitrocellulose surface, and, furthermore, along the native thick filaments passing over their central bare zone. These observations indicate that the myosin molecule has a considerable flexibility in interacting with actin filaments.