β-Carotene is the precursor of vitamin A1.
Oxidation at C-15 converts retinol to the aldehyde, retinal, and further oxidation produces retinoic acid, a hormone that regulates gene expression. 

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β-Carotene is the precursor of vitamin A1.
Oxidation at C-15 converts retinol to the aldehyde, retinal, and further oxidation produces retinoic acid, a hormone that regulates gene expression. 

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#Id: 9351

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RII exhibits constitutive kinase activity; means it is active even when not bound to TGF-β.

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RIII, also called β-glycan, is a cell-surface proteoglycan.

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The function of RIII for TGF-β receptors is similar to that of the α subunit of the IL-2 receptor 

(means facilitating TGF-β binding to the RII and RI)

   

         

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Most cells lack RIII, TGF-β binds directly to the RII

dimer, but Active RII kinase activity is not sufficient to generate an intracellular signal

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RI will not bind to RII unless RII is bound to TGF-β.

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RII phosphorylates serine and threonine in the juxtamembrane segment of the RI (ligand induced receptor hetero-oligomerization), releasing the inhibition of RI kinase activity.