What are the four component proteins of muscle cells, which compose the sarcomere? Describe how they...

What are the four component proteins of muscle cells, which compose the sarcomere? Describe how they interact with one another and allow for muscle contractions.

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Expert Solution

mainly there are two filaments which are involved in muscle contraction- thick filament or thin filament.
th thick filament myosin (globular protein) contains two polymerised portions- heavy meromyosin and light meromyosin. of which the two heavy chains coils, forming globular structure called myosin head at one end.
myosin filaments are linked to Z lines by titin- which is a elastic protein.
The thin filament contains mainly three proteins - actin, tropomyosin and troponin.
Actin- they forms the backbone of thin filament. It is a double helix structure. Basic unit is F actin molecule. G-actin molecules form each strand of these F actin strands.
It is te function of G actin to provide active binding site to myosin head.
Tropomyosin- Thread like proteins which are observed along the groove of actin spiral. it covers the actin sites thatt binds with cross bridges during the resting stage . And thus prevent the binding between myosin head and binding site.
Troponin- it is a globular molecule, which bnds to a particular site on the tropomyosin. They have an important role in causing muscle contraction. They are composed of 3 polypeptide units. 1) Troponin T- it has site for attachment with tropomyosin. It has high affinity for tropomyosin. 2) Troponin- I - they inhibit actin activated myosin ATPase activity during resting stage. they can readily bind with actin ad tropomyosin. 3) Troponin- C- one molecule can bind with 4 Ca2+ ions. tey have got igh Ca 2+ affinity. they triggers the intiation of muscle contraction by combining of Ca2+ ions with troponin,
With the stimulation, a high level of Ca2+ is released from cisternaes. Which causes the Ca2+ ions readily to combine with tropnin C of troponin- tropomyosin complex (which during resting stage covers the G actin for binding with myosin). Thus conformational change occurs, making tropomyosin to go deeper into the groove. thus the G-actins are exposed to form cross bridges with myosin head. thus intiating muscle contraction.

Sydney Mullin answered 1 year ago

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