TGF-Beta Receptor | Structure and Dimerization 

The Transforming Growth Factor beta (TGFβ) receptors are a family of serine/threonine kinase receptors involved in TGF beta signaling pathway. These receptors bind growth factor and cytokine signaling proteins in the TGF-beta family such as TGFβs (TGFβ1, TGFβ2, TGFβ3), bone morphogenetic proteins (BMPs), growth differentiation factors (GDFs), activin and inhibin, myostatin, anti-Müllerian hormone (AMH), and NODAL.
The TGF beta ligand binds to a type II receptor dimer, which recruits a type I receptor dimer forming a hetero-tetrameric complex with the ligand.[4] These receptors are serine/threonine kinase receptors. They have a cysteine rich extracellular domain, a transmembrane domain and a cytoplasmic serine/threonine rich domain. The GS domain of the type I receptor consists of a series of about thirty serine-glycine repeats.The binding of a TGF beta family ligand causes the rotation of the receptors so that their cytoplasmic kinase domains are arranged in a catalytically favorable orientation. The Type II receptor phosphorylates serine residues of the Type I receptor, which activates the protein.
The TGF beta superfamily of ligands include: Bone morphogenetic proteins (BMPs), Growth and differentiation factors (GDFs), Anti-müllerian hormone (AMH), Activin, Nodal and TGFβ's.Signaling begins with the binding of a TGF beta superfamily ligand to a TGF beta type II receptor. The type II receptor is a serine/threonine receptor kinase, which catalyzes the phosphorylation of the Type I receptor. Each class of ligand binds to a specific type II receptor.In mammals there are seven known type I receptors and five type II receptors.