Myosin is a motor protein filament found in muscle tissue. Together with actin filaments, myosin provides the mechanism for muscle contraction, utilizing energy from ATP. The specific conformational rearrangements throughout the chemo-mechanical transduction process are still not known.

The Muscle is composed of single muscle cells (sometimes known as "muscle fibers"). Within the cells are myofibrils; the basic unit of a the contractile apparatus of a myofibril is the sarcomere, which is composed of three different filament systems, the thin filaments assembled by actin proteins, the thick filament system consisting of myosin as well as the elastic filament system composed of the giant protein titin.