Troponin I is part of a heteromeric thin filament regulatory complex that governs skeletal and cardiac muscle contraction. Troponin I is composed of three subunits: troponin I (TnI), troponin T (TnT), and troponin C (TnC), and each of these components plays a different functional role. For example, TnI is an inhibitory component, and confers calcium-sensitivity to the ATPase activity of the myofibril contractile apparatus within striated muscles. Through blocking actin-myosin interactions, TnI modulates muscle relaxation.
