Three types of Smad proteins function in the TGF-β signaling pathway: 

R-Smads (Smad2 and Smad3)

Co-Smads (Smad4)

I-Smads (Smad7)

TLS Online TPP Program

#Id: 1339

#XL - T Zoology

The function of a growth factor-  stabilize receptor dimerization

TLS Online TPP Program

#Id: 1340

#XL - T Zoology

HER1 & HER4, can form stable homodimers after binding a growth factor.

TLS Online TPP Program

#Id: 1341

#XL - T Zoology

HER2 can signal only by forming heterodimers with ligand-bound HER1, HER3, or HER4

TLS Online TPP Program

#Id: 1342

#XL - T Zoology

HER3 lacks a functional kinase domain

TLS Online TPP Program

#Id: 1343

#XL - T Zoology

RAS is a small monomeric G-proteins.

TLS Online TPP Program

#Id: 1344

#XL - T Zoology

RAS is connected to the membrane by a prenylated (lipid) tail.