Myosin

Myosin is a contractile protein filament found in muscle tissue. Together with actin filaments, myosin provides the mechanism for muscle contraction, utilizing energy from ATP.

Muscle is composed of muscle cells (sometimes known as "muscle fibers"). Within the cells are myofibrils; myofibrils contain sarcomere, which is composed of actin and myosin. Muscle cells are grouped together into bundles of fascicle; the bundles are then grouped together to form muscle.