Myosin is a 480,000 dalton protein containing two identical heavy chains (200,000 daltons each) and four light chains (15,000-26,000 daltons). Myosin molecules consist of two major regions: tails (rods) and heads; they aggregate into filaments through the tail region. Multiple forms of myosin heavy chains exist for each muscle type; skeletal, cardiac, smooth and non-muscle isomyosin forms exist in different types of skeletal muscle, depending on the physiological function of the muscle.
