Scanning Electron Microscopy of the Myosin-Coated Surface of Polystyrene Beads in a Force-Movement Assay System for ATP-Dependent Actin-Myosin Sliding

We examined the myosin-coated surface of polystyrene beads, which slide on actin filaments in the presence of ATP with characteristics essentially similar to those of contracting muscle, using a high-resolution scanning electron microscope (JSM-890, JEOL). The bead surface was mostly covered with myosin filaments (diameter, 15-45 nm) with helically arranged myosin heads. Considering the amount of force generated by the myosin heads on the bead (∼ 10 pN), this result indicates that the bead movement may be caused by about 10 myosin heads within a short myosin filament segment, but not by randomly oriented myosin heads