Upf1 is the first NMD protein to act, binding to the terminating ribosome—specifically to its release factor complex.

TLS Online TPP Program

#Id: 9350

#Unit 4. Cell Communication and Cell Signaling

RI and RII receptors are homodimeric proteins with serine/threonine kinases in their cytosolic domains. 

(RI and RII sufficient to serve as a functional hetero-tetrameric TGF-β receptor)

TLS Online TPP Program

#Id: 9351

#Unit 4. Cell Communication and Cell Signaling

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

TLS Online TPP Program

#Id: 9352

#Unit 4. Cell Communication and Cell Signaling

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

TLS Online TPP Program

#Id: 9353

#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)

   

         

TLS Online TPP Program

#Id: 9355

#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

TLS Online TPP Program

#Id: 9356

#Unit 4. Cell Communication and Cell Signaling

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