Canadian Medical Guide > Chemicals and Drugs > Amino Acids, Peptides, and Proteins > Proteins > Contractile Proteins > Muscle Proteins Terms and Definitions

Muscle Proteins

Medical Definition:	The protein constituents of muscle, the major ones being ACTINS and MYOSINS. More than a dozen accessary proteins exist including TROPONIN; TROPOMYOSIN; and DYSTROPHIN.
Guide Notes:	/biosyn /drug eff /physiol permitted; for contractile proteins in muscle, index only under MUSCLE PROTEINS or specifics & not also under CONTRACTILE PROTEINS

Muscle Proteins Categories.

	Actinin - A protein factor that regulates the length of R-actin. It is chemically similar, but immunochemically distinguishable from actin.
	Actins - Filamentous proteins that are the main constituent of the thin filaments of muscle fibers. The filaments (known also as filamentous or F-actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 amino acids long. This is known as globular or G-actin. In conjunction with MYOSINS, actin is responsible for the contraction and relaxation of muscle.
	Actomyosin - A protein complex of actin and MYOSINS occurring in muscle. It is the essential contractile substance of muscle.
	Dystrophin - A muscle protein localized in surface membranes which is the product of the Duchenne/Becker muscular dystrophy gene. Individuals with Duchenne muscular dystrophy usually lack dystrophin completely while those with Becker muscular dystrophy have dystrophin of an altered size. It shares features with other cytoskeletal proteins such as SPECTRIN and alpha-actinin but the precise function of dystrophin is not clear. One possible role might be to preserve the integrity and alignment of the plasma membrane to the myofibrils during muscle contraction and relaxation. MW 400 kDa.
	Myogenic Regulatory Factors - A family of muscle-specific transcription factors which bind to DNA in control regions and thus regulate myogenesis. All members of this family contain a conserved helix-loop-helix motif which is homologous to the myc family proteins. These factors are only found in skeletal muscle. Members include the myoD protein (MYOD PROTEIN); MYOGENIN; myf-5, and myf-6 (also called MRF4 or herculin).
	Myoglobin - A conjugated protein which is the oxygen-transporting pigment of muscle. It is made up of one globin polypeptide chain and one heme group.
	Tropomyosin - A protein found in the thin filaments of muscle fibers. It inhibits contraction of the muscle unless its position is modified by TROPONIN.
	Troponin - One of the minor protein components of skeletal muscle. Its function is to serve as the calcium-binding component in the troponin-tropomyosin B-actin-myosin complex by conferring calcium sensitivity to the cross-linked actin and myosin filaments.

Muscle Proteins Medical Definitions and Terms

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