Troponin I is part of a heteromeric complex playing an important role in the regulation of skeletal and cardiac muscle contraction. It consists of three subunits, troponin I (TnI), troponin T (TnT) and troponin C (TnC). Each subunit is responsible for part of troponin complex function. TnI inhibits ATPase activity of acto myosin and TnT and TnI are present in cardiac muscles in different forms than in skeletal muscles. Only one tissue specific isoform of TnI is described for cardiac muscle tissue (cTnI) and this is expressed only in myocardium.
