title: Bidirectional movement of actin filaments along tracks of myosin heads.
abstract: It is well established that muscle contraction results from the relative sliding of actin and myosin filaments. Both filaments have definite polarities and well-ordered structures. Thick filaments, however, are not vital for supporting movement in vitro. Previously we have demonstrated that actin filaments can move continuously on myosin fragments (subfragment-1 or heavy meromyosin (HMM] that are bound to a nitrocellulose surface. Here we report that actin filaments can move in opposite directions on tracks of myosin heads formed when actin filaments decorated with HMM are placed on a nitrocellulose surface. The actin filaments always move forward, frequently changing the direction of the movement, but never move backward reversing the polarity of the movement. The direction of movement is therefore determined by the polarity of the actin filament. These results indicate that myosin heads have considerable flexibility.
authors.affiliation: Department of Cell Biology, Stanford University School of Medicine, California 94305.
authors.forename: Y Y
authors.initials: YY
authors.lastname: Toyoshima
authors.forename: C
authors.initials: C
authors.lastname: Toyoshima
authors.forename: J A
authors.initials: JA
authors.lastname: Spudich
mesh_terms: D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D000255:Adenosine Triphosphate / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D008854:Microscopy, Electron; D015879:Myosin Subfragments / Q000378:metabolism; D009218:Myosins / Q000378:metabolism* / Q000648:ultrastructure; D010446:Peptide Fragments / Q000378:metabolism
chemical_list: D000199:Actins; D015879:Myosin Subfragments; D010446:Peptide Fragments; D000255:Adenosine Triphosphate; D009218:Myosins