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Tropomyosin Tropomyosin is an alpha-helical protein that forms a coiled-coil structure of 2 parallel helices containing 2 sets of 7 alternating actin binding sites. The protein is best known for its role in regulating the interaction between actin and myosin in muscle contraction, but is also involved in the organization and dynamics of the cytoskeleton in non-muscle cells. There are multiple cell-specific isoforms, expressed by alternative promoters and alternative RNA processing of at least four genes. Muscle isoforms of tropomyosin are characterized by having 284 amino acid residues and a highly conserved N-terminal region, whereas non-muscle forms are generally smaller and are heterogeneous in their N-terminal region.
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