Three types of troponins exist—troponin I, troponin T, and troponin C. Each of the 3 troponin subunits has a unique function. Troponin T binds the troponin components to tropomyosin. Troponin I inhibits the interaction of myosin with actin. Troponin C contains the binding sites for the Ca2+ that helps to initiate contraction.(8)