Myosinbinding

Myosin binding refers to interactions between the motor protein myosin and other proteins that bind to myosin, influencing its function, localization, and regulation. These interactions occur in muscle tissue, where myosin powers contraction, and in non-muscle cells, where myosin motors organize cytoskeletal networks and transport cargo. Binding can involve different regions of myosin, including the head, neck, or tail, and is frequently regulated by phosphorylation, calcium levels, and the nucleotide state of myosin.

In striated muscle, the best-characterized myosin-binding protein is myosin-binding protein C (MyBP-C). Located in the C-zone of the sarcomeric A-band, MyBP-C binds to the myosin thick filament and can interact with actin as well. Through these contacts, it modulates cross-bridge cycling by influencing the availability of myosin heads for attachment to actin, thereby affecting force production and contraction rate. Phosphorylation of MyBP-C can relieve its inhibitory effects, accelerating contraction. Mutations in MYBPC3 are a major cause of familial hypertrophic cardiomyopathy.

Beyond sarcomeres, myosin-binding interactions coordinate cargo transport and cytoskeletal organization in non-muscle cells. A well-studied example is the Rab27a–melanophilin–myosin Va complex in pigment cells, which links melanosomes to myosin Va for directed transport. Other myosin-binding partners include adaptor and scaffolding proteins that recruit myosin to membranes, vesicles, or actin networks. These interactions are regulated by signaling pathways and cellular energy status, ensuring proper timing and directionality of movement.

Understanding myosin-binding relationships helps explain how motor activity is integrated with cellular processes and how disruptions can contribute to disease, informing models of muscle mechanics and intracellular transport.