[Cardiac contractile proteins].

Structure and function of cardiac contractile proteins were summarized in connection with the pathophysiology of the heart muscle. Myosin is a large molecule consisting of two heavy chains and four light chains. Functional domains including ATP binding and actin binding sites reside in heavy chain. Heavy chain has two functionally distinct isoforms and their relative content changes in response to various pathological stimuli. The structure of myosin heavy chain also plays an important role in pathogenesis of familial hypertrophic cardiomyopathy. Another component of contractile machine is the F-actin, polymer of actin molecules. Actin is also a polymorphic protein and its expression changes under various conditions. However, the functional significance of actin polymorphism is yet to be determined.