Related Experiment Video
Updated: May 9, 2026

Probing Myosin Ensemble Mechanics in Actin Filament Bundles Using Optical Tweezers
Published on: May 4, 2022
The myosin start-of-power stroke state and how actin binding drives the power stroke
Matthias Preller1, Kenneth C Holmes
1Institute for Biophysical Chemistry, Hannover Medical School, Hannover, Germany; Centre for Structural Systems Biology (CSSB), German Electron Synchrotron (DESY), Hamburg, Germany.
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.
Related Concept Videos
Actin and Myosin in Muscle Contraction
Cross-bridge Cycle
Excitation-Contraction Coupling in Skeletal Muscles
When an action potential...
Overview of Myosin Structure and Function
ATP Synthase: Mechanism
The Sarcomere
Each myosin...
