title: The myosin start-of-power stroke state and how actin binding drives the power stroke.
abstract: We propose that on binding to actin at the start of the power stroke the myosin cross-bridge takes on the rigor configuration at the actin interface. Starting from the prepower stroke state, this can be achieved by a small movement (16° rotation) of the lower 50K domain without twisting the central β-sheet or opening switch-1 or switch-2. The movement of the lower 50K domain puts a strain on the W-helix. This strain tries to twist the β-sheet, which could drive the power stroke. This would provide a coupling between actin binding and the execution of the power stroke. During the power stroke the β-sheet twists, moving the P-loop away from switch-2, which opens the nucleotide binding pocket and separates ADP from Pi . The power stroke is different from the recovery stroke because the upper and lower 50K domains are tethered in the rigor configuration.
authors.affiliation: Institute for Biophysical Chemistry, Hannover Medical School, Hannover, Germany; Centre for Structural Systems Biology (CSSB), German Electron Synchrotron (DESY), Hamburg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Preller
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Holmes
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D004023:Dictyostelium / Q000378:metabolism*; D008958:Models, Molecular; D024462:Myosin Type II / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D000199:Actins; D024462:Myosin Type II
keywords: Lymn-Taylor cycle; modeling; muscle; myosin; start-of-power stroke; structure; targeted molecular dynamics