Myosin is a motor protein filament found in muscletissue. Together with actin filaments, myosin provides the mechanism for muscle contraction, utilizing energy from ATP. The specific conformational rearrangements throughout the chemo-mechanical transduction process are still not known.
The Muscle is composed of single muscle cells (sometimes known as "muscle fibers"). Within the cells are myofibrils; the basic unit of a the contractile apparatus of a myofibril is the sarcomere, which is composed of three different filament systems, the thin filaments assembled by actin proteins, the thick filament system consisting of myosin as well as the elastic filament system composed of the giant protein titin.
Myosins are class of eight molecular motor proteins found in eukaryote tissues.
It is one of the key motor systems in cells; it is best known that myosin II plays a major role in both muscle contractions and cytokinesis.
Other members of the myosin family have other purposes as well; myosin I and V participate in the transport of membrane vesicles while myosins VI, VII, and XV have functions related to hearing and hair cell stereocilia structure.
By labeling a myosin VI on the head (green), or on the neck (red), and localizing the dye within a few nanometers, scientists determined that myosin walks "hand-over-hand," while causing a part of the protein to come undone.
Myosin VI is a reverse-direction molecular motor that moves materials to various locations within a living cell.
Surprisingly, myosin VI has a step size that is highly variable, but on average is nearly as large as that of myosin V, which has a lever arm that is three times longer.
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