A single myosin head moves along an actin filament with regular steps of 5.3 nanometres

Actomyosin, a complex of actin filaments and myosin motor proteins, is resp onsible for force generation during muscle contraction. To resolve the indi vidual mechanical events of force generation by actomyosin, we have develop ed a new Instrument with which we can capture and directly manipulate indiv idual myosin subfragment-1 molecules using a scanning probe. Single subfrag ment-1 molecules can be visualized by using a fluorescent label. The data t hat we obtain using this technique are consistent with myosin moving along an actin filament with single mechanical steps of approximately 5.3 nanomet res; groups of two to five rapid steps In succession often produce displace ments of 11 to 30 nanometres. This multiple stepping is produced by a singl e myosin head during just one biochemical cycle of ATP hydrolysis.