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"A-band" redirects here. For other uses of the term see A band.
A sarcomere (Greek sárx = "flesh", méros = "part") is the basic unit of a muscle's cross-striated myofibril. Sarcomeres are multi-protein complexes composed of three different filament systems.
- The thick filament system is composed of myosin protein which is connected from the M-line to the Z-disc by Titin It also contains myosin-binding protein C which binds at one end to the thick filament and the other to Actin.
- The thin filaments are assembled by actin monomers bound to nebulin. Which also involves tropomyosin; a dimer which coils itself around the F-actin core of the thin filament.
- Nebulin and Titin gives stability and structure to the sarcomere.
A muscle cell from a bicep may contain 100,000 sarcomeres. The myofibrils of smooth muscle cells are not arranged into sarcomeres.
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