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Figure 1. TGF-ß receptor activation. TGF-ß initiates signaling by the assembly of receptor complexes involving two transmembrane serine-threonine kinase receptors (TßR-I and TßR-II). Following binding of TGF-ß to TßR-II, TßR-I is recruited to form a heterotetrameric complex and is phosphorylated at serine residues within its GS domain by the constitutively active TßR-II. The activated TßR-I then activates a cascade of downstream signaling events that ultimately regulates gene transcription.
