cTnI has an apparent molecular weight of 22.5 kDa. cTnI is a candidate marker with acceptable sensitivity and specificity for AMI and other cardiac diseases. Troponin, a molecule that binds to the thin filament (actin) of striated muscle fibers, acts with intracellular calcium to control the interaction of the thin filament with the thick filament (myosin), thus regulating muscle contraction. Troponin I prevents muscle contraction in the absence of calcium, which has two skeletal muscle isoforms with considerable amino acid sequence homology. cTnI contains an additional N-terminal sequence and is highly specific for myocardium.
