Myosin-7 (MYH7, also named Myosin heavy chain, cardiac muscle β isoform) is an actin-based motor molecule with ATPase activity essential for muscle contraction. Several mutations in MYH7 are frequent causes of hypertrophic cardiomyopathy (HCM), a disease characterized by hypercontractility and eventual hypertrophy of the left ventricle. Many HCM-causing mutations appear to reduce myosin's ability to form an autoinhibited state. In an autoinhibited state, the myosin heads fold back onto their own subfragment 2 (S2) tail in a conformation known as the interacting heads motif (IHM). One of the two heads in the dimer has its actin-binding interface buried in the folded structure; this head is referred to as the blocked head, while the other is called the free head, since its actin-binding interface is not hidden structurally. Many myosin types have the folded back IHM structure. The IHM structure correlates to an ultra-low basal ATPase rate in the absence of an action called the 'super relaxed state'. Heads lacking the S2 tail mostly have a faster basal ATPase rate referred to as the 'disordered relaxed state'. Especially, mutations in the myosin lever arm or the pliant region of the lever arm can affect myosin function either by altering its intrinsic motor activity, and/or reducing its ability to form the autoinhibited state.