Video imaging of walking myosin V by high-speed atomic force microscopy

The dynamic behaviour of myosin V molecules translocating along actin filaments has been mainly studied by optical microscopy. The processive hand-over-hand movement coupled with hydrolysis of adenosine triphosphate was thereby demonstrated. However, the protein molecules themselves are invisible in the observations and have therefore been visualized by electron microscopy in the stationary states. The concomitant assessment of structure and dynamics has been unfeasible, a situation prevailing throughout biological research. Here we directly visualize myosin V molecules walking along actin tracks, using high-speed atomic force microscopy. The high-resolution movies not only provide corroborative ‘visual evidence’ for previously speculated or demonstrated molecular behaviours, including lever-arm swing, but also reveal more detailed behaviours of the molecules, leading to a comprehensive understanding of the motor mechanism. Our direct and dynamic high-resolution visualization is a powerful new approach to studying the structure and dynamics of biomolecules in action. Walking myosin V caught on video Motor proteins of the myosin family serve many important functions in eukaryotic cells and are central to actin-based motility. Our understanding of the mechanism of myosin action has been hampered by the lack of technology for simultaneously observing the structure and dynamics of biomolecules, but now Kodera et al . have used high-speed atomic force microscopy (HS-AFM) to directly observe myosin V moving along actin filaments with unprecedented time resolution. They obtain high-resolution movies that provide visual evidence supporting the 'swinging lever-arm' model for myosin motility. The high-resolution imaging possible using HS-AFM should make the technique broadly applicable in the fields of structural biology and single-molecule biology. High-speed atomic force microscopy can be used to record the structure and dynamics of biomolecules simultaneously. These authors use this method to directly observe the dynamics of the motor protein myosin V moving along actin filaments, with unprecedented time resolution. The high-resolution movies provide evidence supporting the 'swinging lever-arm' model of myosin motility, and provide important insights into the mechanism of motor movement.