Myosin, calcium activated from porcine heart has been used in the induction of experimental autoimmune myocarditis (EAM).
A protein, of molecular weight above500,000, that is an essential component of mus-cular tissue and strongly affects its contractileproperties.
Myosin is one of three classes of cytoskeletal motor proteins that have been identified. The others are kinesins and dyneins. Myosin family members contain globular head domain with actin and ATP binding site, α-helical neck region and a coiled–coiled tail domain. Nonmuscle myosins are highly expressed in brain.
Myosin and actin are the principal fibrous proteins of
muscle, having molecular weights above 500,000. Their
interaction brings about muscle contraction.
Myosin interacts with actin in muscle and non-muscle cells. Myosin molecules consist of two major regions: tails (rods) and heads. They aggregate into filaments through the tail region and interact with actin and with ATP through the head region. Myosin molecules spontaneously assemble into filaments in solutions of physiologic ionic strength and pH. Thick filament consists mainly of myosin molecules. Myosin is activated by the enzyme ATPase. This activation is the immediate source of the free energy that drives muscle contraction. It binds to the polymerized form of actin, the major constituent of the thin filament. 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. These are designated as type I (slow-twitch) and type II (fast-twitch). Myosin is one of three classes of cytoskeletal motor proteins that have been identified. The others are kinesins and dyneins. These three types of proteins are thought to be responsible for the many movements that occur in cells. Myosin has been shown to be involved in neurosensory function, vesicle trafficking, determinant partitioning, and cortical function.
