Phalloidin 

isolated from Amanita phalloides, binds at the interface between subunits in F-actin, locking adjacent subunits together and preventing depolymerization.

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#Unit 4. Cell Communication and Cell Signaling

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

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#Unit 4. Cell Communication and Cell Signaling

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

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#Unit 4. Cell Communication and Cell Signaling

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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#Unit 4. Cell Communication and Cell Signaling

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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#Unit 4. Cell Communication and Cell Signaling

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

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#Unit 4. Cell Communication and Cell Signaling

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