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tropomyosin

(Science: protein) protein (66 kD) associated with actin filaments both in cytoplasm and (in association with troponin) in the thin filament of striated muscle.

Composed of two elongated _ helical chains (each about 33 kD), 40 nm long, 2 nm diameter. Each chain has six or seven similar domains and interacts with as many g actin molecules as there are domains.

Not only does the binding of tropomyosin stabilise the f actin, but the association with troponin in striated muscle is important in control by calcium ions.