MyosinHeavyChainIsoformen

Myosin heavy chain (MHC) refers to the motor protein subunits that comprise the thick filaments of conventional myosin II found in muscle. In vertebrates, a family of MHC genes encodes multiple isoforms that are differentially expressed in cardiac muscle and skeletal muscle, contributing to varied contractile properties.

Each myosin II molecule is a hexamer consisting of two identical heavy chains and two pairs of light chains. The heavy chains form a dimer with a long coiled-coil tail and a globular head that contains an ATPase site and an actin-binding site. The energy from ATP hydrolysis drives conformational changes that generate movement along actin filaments.

Genes encoding MHCs are part of the myosin gene family. In mammals, the heart mainly expresses MYH6 and MYH7, while skeletal muscle expresses multiple fast and slow isoforms derived from several MYH genes, with expression patterns that reflect fiber type, development, and training.

Changes in MHC expression occur during development, aging, and in disease. Mutations in MHC genes, particularly in MYH7, are associated with inherited cardiomyopathies such as hypertrophic and dilated forms. Altered MHC composition also influences muscle performance and disease progression.

Research into MHC isoforms informs our understanding of muscle physiology, cardiac function, and muscle-related diseases, and has implications for diagnostics and therapeutic approaches.