Myosin-7 (Cardiac myosin heavy chain beta) (MYH7)

Myosin-7, also known as cardiac myosin heavy chain beta, is the primary molecular motor protein in the human heart and slow-twitch skeletal muscle. It functions by converting chemical energy from ATP hydrolysis into mechanical force, enabling the sliding of thick and thin filaments during muscle contraction. The concept of "myosin homeostasis" refers to the critical physiological balance of myosin protein levels, proper folding by chaperones (such as UNC-45 and HSP90), and the transition of myosin heads between an active force-producing state and a "super-relaxed" (SRX) state [11, 17]. In diseases like hypertrophic cardiomyopathy (HCM), genetic mutations in MYH7 disrupt this homeostasis, typically leading to an excess of active myosin heads and myocardial hypercontractility [2, 5]. Modern therapeutic agents like mavacamten and aficamten act as allosteric inhibitors of the cardiac myosin ATPase, restoring homeostasis by shifting the myosin population toward the relaxed state to reduce excessive cross-bridging and alleviate ventricular obstruction [3, 4]. Conversely, activators like omecamtiv mecarbil are used to enhance myosin function in conditions characterized by reduced contractility, such as heart failure with reduced ejection fraction [6, 7].

Other names

Myosin homeostasisCardiac myosin heavy chain betaBeta-myosin heavy chainMYH7MyHC-betaSarcomeric myosinMyosin-7

Allosteric modulation of cardiac myosin ATPase to regulate the transition of myosin heads between active and super-relaxed (SRX) states, thereby normalizing myocardial contractility and relaxation [2, 5].