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class V myosin, motor domain Myo5, also called heavy chain 12, myoxin, are dimeric myosins that transport a variety of intracellular cargo processively along actin filaments, such as melanosomes, synaptic vesicles, vacuoles, and mRNA. The catalytic (head) domain has ATPase activity and belongs to the larger group of P-loop NTPases. It also contains a IQ domain and a globular DIL domain. Myosin V is a class of actin-based motor proteins involved in cytoplasmic vesicle transport and anchorage, spindle-pole alignment and mRNA translocation. The protein encoded by this gene is abundant in melanocytes and nerve cells. Mutations in this gene cause Griscelli syndrome type-1 (GS1), Griscelli syndrome type-3 (GS3) and neuroectodermal melanolysosomal disease, or Elejalde disease. Multiple alternatively spliced transcript variants encoding different isoforms have been reported, but the full-length nature of some variants has not been determined. Myosins are actin-dependent molecular motors that play important roles in muscle contraction, cell motility, and organelle transport. The head domain is a molecular motor, which utilizes ATP hydrolysis to generate directed movement toward the plus end along actin filaments. A cyclical interaction between myosin and actin provides the driving force. Rates of ATP hydrolysis and consequently the speed of movement along actin filaments vary widely, from about 0.04 micrometer per second for myosin I to 4.5 micrometer per second for myosin II in skeletal muscle. Myosin II moves in discrete steps about 5-10 nm long and generates 1-5 piconewtons of force. Upon ATP binding, the myosin head dissociates from an actin filament. ATP hydrolysis causes the head to pivot and associate with a new actin subunit. The release of Pi causes the head to pivot and move the filament (power stroke). Release of ADP completes the cycle. Note that the Dictyostelium myoVs are not contained in this child group. CyMoBase classifications were used to confirm and identify the myosins in this hierarchy. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",