Troponin, working in conjunction with tropomyosin, functions as a molecular switch, regulating muscle contraction in response to changes in the intracellular Ca2+ concentration. Troponin consists of three subunits, the Ca2+-binding subunit troponin C (TnC), the tropomyosin-binding subunit troponin T (TnT), and the inhibitory subunit troponin I (TnI). Troponin I binds to actin in thin myofilaments to hold the actin-tropomyosin complex in place, because of which myosin cannot bind to actin in relaxed muscle. When Calcium binds to the Troponin C it causes certain confomational changes which leads to dislocation of troponin I. The letter “I” is given due to its inhibitory character.