Vertebrate skeletal muscle contraction, also depends on set of specialized accessory proteins that are closely associated with the actin thin filaments:

a) Tropomyosin

b) Troponin

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Activated RTKs and cytokine receptors promote PLCγ activity in two ways: 

By localizing PLCγ to the membrane

By phosphorylating PLCγ

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The SH2 domains of PLCγ bind to specific phosphotyrosines on the activated RTKs and cytokine receptors, thus positioning PLCγ close to PIP2.

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Kinase activity associated with receptor activation phosphorylates tyrosines on the bound PLCγ, enhancing its hydrolase activity. 

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Activated RTKs and cytokine receptors initiate another phosphoinositide pathway by recruiting PI-3 kinase to the cytosolic surface of the plasma membrane.

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PI-3 kinase contains SH2 domain which binds to phosphotyrosines on the activated RTKs and cytokine receptors

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PI-3 kinase adds a phosphate to the 3′ carbon in one of two separate PI substrates, leading to formation of two PI 3-phosphates: PI(3,4)P2 or PI(3,4,5)P3