Troponin complex (Tn (or cTn for cardiac-specific forms))

Troponin is a heterotrimeric regulatory protein complex composed of three distinct subunits—troponin C (TnC), troponin I (TnI), and troponin T (TnT)—that plays an essential role in the regulation of skeletal and cardiac muscle contraction. The complex is located on the thin filaments of striated muscles alongside actin and tropomyosin. Each subunit has a specific function: * Troponin C binds calcium ions to initiate conformational changes necessary for contraction. * Troponin I inhibits actomyosin ATPase activity by blocking myosin-binding sites on actin. * Troponin T anchors the troponin complex to tropomyosin. Upon an increase in intracellular calcium concentration during excitation-contraction coupling, calcium binds to troponin C. This triggers structural rearrangements that move tropomyosin away from myosin-binding sites on actin filaments, allowing crossbridge formation between actin and myosin which leads to muscle contraction. When calcium levels fall, these processes reverse leading to relaxation[1][4][5][6]. There are multiple isoforms encoded by different genes that are tissue-specific; notably cardiac-specific forms (cardiac troponins I [cTnI], cardiac troponins T [cTnT]) serve as highly sensitive clinical biomarkers for diagnosing heart damage such as myocardial infarction or myocarditis when detected at elevated levels in blood serum[4][6]. Mutations affecting any component can cause inherited cardiomyopathies. Note: "Troponin" refers collectively to this multi-subunit regulatory protein rather than a single molecular target such as an enzyme or receptor; it is not itself considered a direct therapeutic target but rather serves primarily as a diagnostic biomarker in clinical practice.

Other names

TroponinTroponin complexTnCardiac troponin (cTn)Skeletal muscle troponin