Troponin

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Troponin

Troponin (/trɒˈpoʊnɪn/ troh-POH-nin) is a complex of three regulatory proteins (troponin C, troponin I, and troponin T) that is integral to muscle contraction in skeletal muscle and cardiac muscle, but not smooth muscle.

Etymology

The term "troponin" derives from the Greek "tropos" meaning "turn" and "ninos" meaning "sinew" or "tendon". It was first identified in 1965 by Ebashi and Kodama.

Function

Troponin is attached to the protein tropomyosin and lies within the groove between actin filaments in muscle tissue. In a relaxed muscle, tropomyosin blocks the attachment site for the myosin crossbridge, thus preventing contraction. When the muscle cell is stimulated to contract by an action potential, calcium channels open in the sarcoplasmic reticulum and release calcium into the sarcoplasm. Some of this calcium attaches to troponin, which causes it to change shape, exposing the binding sites on the actin filaments and allowing contraction to occur.

Clinical significance

Troponin is very sensitive and specific to myocardial damage. The measurement of troponin in blood can be used in the diagnosis of myocardial infarction (heart attack). Troponin levels can become significantly elevated in the blood within 3 to 6 hours after injury to the heart and can remain elevated for 10 to 14 days.

Related terms

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