Myosiin

Myosiin is commonly a misspelling of myosin, a large family of ATP-dependent motor proteins that interact with actin to generate mechanical force in eukaryotic cells. Myosins convert the energy from ATP hydrolysis into directed movement along actin filaments and play essential roles in muscle contraction, cellular transport, and cell motility.

Myosin proteins share a conserved motor domain that binds and hydrolyzes ATP, a neck region that binds light chains and acts as a lever, and a tail domain that determines dimerization and cargo binding. In conventional muscle, class II myosins assemble into thick filaments and participate in the cross-bridge cycle with actin to produce contraction. Non-muscle myosins power processes such as organelle transport, vesicle trafficking, membrane dynamics, and cargo repositioning, often moving toward the barbed end of actin or toward specific cellular destinations.

Genetically, myosins are encoded by multiple gene families. In humans, heavy chains are encoded by MYH genes and light chains by MYL genes. Mutations in certain myosin genes, notably MYH7 and MYH6, are linked to cardiomyopathies; other myosin mutations contribute to skeletal muscle diseases and hearing disorders in some contexts.

Beyond muscle, myosins are diverse and ubiquitous, enabling intracellular movement in yeast to complex transport in neurons. Research on myosins informs understanding of motor protein mechanics, cytoskeletal dynamics, and disease mechanisms.