Myosin is a 480 kD protein that interacts with actin in muscle contraction and in a wide range of other eukaryotic motility processes. Conventional myosin contains two identical heavy chains (MHC-200kD each) and four light chains (MLC-15-26 kD). Defects in MYL2 cause cardiomyopathy familial hypertrophic type 10, a hereditary heart disorder, and cardiomyopathy familial hypertrophic with mid-left ventricular chamber type 2, is a very rare variant of familial hypertrophic cardiomyopathy.