Tropomyosin
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Tropomyosin is an alpha helical coiled coil protein dimer.
It binds end to end along F actin filaments in striated muscle.
Tropomyosin blocks myosin binding and hence crossbridge cycling in the absence of Ca2+ and the muscle Ca2+ regulatory element troponin.
Ca2+ influx from the sarcoplasmic reticulum of striated muscle myocytes binds to troponin and subsequently moves tropomyosin on the F-actin filament exposing the myosin binding sites.
Whilst recent structural visualisation and kinetic modeling has suggested that myosin binding further moves tropomyosin on actin to a fully open state allowing for uninhibited crossbridge cycling as the muscle contracts.
This three state model of thin filament regulation involving tropomyosin and troponin is still debated by experts who believe that two state regulation of muscle contraction (involving a blocked and open state) is sufficient to explain current experimental data and models.
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[edit] Sliding filament theory
Tropomyosin has a lot to do with the sliding filament theory which relates to the contraction of the muscular system.
Troponin and tropomyosin together form the tropomyosin protein complex.
This protein complex is very closely related and near the actin filaments that help create sarcomeres, which are part of the muscule structure in whole.
The important attribute of this is that it prevents the muscles from contracting constantly which over time would lead to intense pain.
They disable myosin from constantly connecting with actin unless a chemical reaction with Acetylcholine, which is the neurotransmiter which releases Ca2+, a calcium ion; after electrical stimulus has been applied to the neuron, which releases the Acetylcholine to the nerve synapse.
After the contraction is finished the Ca+ is removed using active transport.
Without the calcium ion attached to the troponin the tropomyosin relaxes and covers the actin binding site.
This keeps the myosin crossbridge from binding with the actin, and therefore the muscle relaxes.
[edit] Allergies
Certain tropomyosins are known to cause allergies in certain people, and those who have cross-reactive allergies can get symptons from a range of sources due to a common allergen found in all these sources.
Common allergies include shrimp, dust mites and mollusks.
[edit] Genes
[edit] External links
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