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Control
of intracellular Ca2+ - principal mechanism that initiates
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contraction and
relaxation in smooth and striated muscle
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Regulatory
pathways:
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striated
muscle-Ca2+ activates contraction by binding to thin
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filament
associated protein, troponin
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smooth
muscle-Ca2+ binds to calmodulin, which then associates
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with the
catalytic subunit of myosin light chain kinase-
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phosphorylates
serine 19 on the regulatory light
chain of
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myosin. Phosphorylation of Ser19 allows the
myosin ATPase to
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be activated by
actin and the muscle to contract.
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