Cardiac myosin binding protein C3 (MyBPC3) is a 140 kDa thick filament-associated protein located in the crossbridge region of cardiac muscle sarcomeres. It is composed of eight Ig-like domains and three fibronectin 3-like domains and is known to be a physiological substrate of cAMP-dependent protein kinase. MyBPC3 has a role in sarcomeric structure and in the regulation of cardiac muscle contraction. MyBPC3 is released into the coronary effluent during myocardial infarction. Mutations in MyBPC3 are associated with hypertrophic cardiomyopathy.