Title: Myosin
Literature References: Mol wt approx 500,000. The main protein in muscle, which, by hydrolyzing ATP, provides the energy necessary for muscular contraction. Individual molecules are rod-shaped and consist of two globular heads attached flexibly to a tail of approx 1500Å length. All muscle myosins have a similar subunit structure composed of two heavy chains and two distinct pairs of light chains. One of the light chains is involved in a Ca2+-dependent regulatory process in the vertebrate skeletal muscle system. Biological prepn and review: A. G. Szent-Györgyi, Chemistry of Muscular Contraction (Academic Press, New York, 2nd ed., 1951) pp 38-57, 146-148. Other reviews: idem, Adv. Enzymol. Relat. Subj. Biochem. 16, 313-360 (1955); A. G. Szent-Györgyi et al., in Sulfur in Proteins, R. Benesch et al., Eds. (Academic Press, New York, 1959) pp 291-295; J. Gergely, Biochemistry of Muscle Contraction (Little, Brown, Boston, 1964) pp 3-115; several authors in Contractile Proteins and Muscle, K. Laki, Ed. (Dekker, New York, 1971); several authors in Methods Enzymol. 85, Part B, 55-130 (1982). Review on structure and function of myosin: W. F. Harrington, "Contractile Proteins of Muscle" in The Proteins vol. 4, H. Neurath, R. L. Hill, Eds. (Academic Press, New York, 1979) p 245-409. Polymorphism of mammalian myosins and distribution of isoforms in different muscle fibers reviewed by A. G. Weeds in Plasticity of Muscle, D. Pette, Ed. (DeGruyter, Berlin, 1980) pp 55-68. Role of myosin light chains in calcium regulation: Kendrick-Jones, Nature 249, 631 (1974). Tertiary crystal structure of globular heads: I. Rayment et al., Science 261, 50 (1993). See also Tropomyosin.
Myricetin Myristic Acid Myristicin Myristyl Alcohol Myristyltrimethylammonium Bromide

Part of the myosin II structure. Atoms in the heavy chain are colored red on the left-hand side, and atoms in the light chains are colored orange and yellow.

Myosins comprise a family of ATP-dependent motor proteins and are best known for their role in muscle contraction and their involvement in a wide range of other eukaryotic motility processes. They are responsible for actin-based motility. The term was originally used to describe a group of similar ATPases found in striated and smooth muscle cells.[1] Following the discovery by Pollard and Korn of enzymes with myosin-like function in Acanthamoeba castellanii, a large number of divergent myosin genes have been discovered throughout eukaryotes. Thus, although myosin was originally thought to be restricted to muscle cells (hence, "myo"), there is no single "myosin" but rather a huge superfamily of genes whose protein products share the basic properties of actin binding, ATP hydrolysis (ATPase enzyme activity), and force transduction. Virtually all eukaryotic cells contain myosin isoforms. Some isoforms have specialized functions in certain cell types (such as muscle), while other isoforms are ubiquitous. The structure and function of myosin is strongly conserved across species, to the extent that rabbit muscle myosin II will bind to actin from an amoeba.[2]