title: Transforming growth factor beta superfamily
text: # Transforming growth factor beta superfamily
  
  The transforming growth factor beta (TGF-β) superfamily is a large group of structurally related cell regulatory proteins that was named after its first member, TGF-β1, originally described in 1983. They interact with TGF-beta receptors.
  
  Many proteins have since been described as members of the TGF-β superfamily in a variety of species, including invertebrates as well as vertebrates and categorized into 23 distinct gene types that fall into four major subfamilies:
  
  * The TGF-β subfamily
  * The bone morphogenetic proteins and the growth differentiation factors
  * The activin and inhibin subfamilies
  * The left-right determination factors
  * A group encompassing various divergent members
  
  Transforming growth factor-beta (TGF-beta) is a multifunctional peptide that controls proliferation, differentiation and other functions in many cell types. TGF-beta-1 is a peptide of 112 amino acid residues derived by proteolytic cleavage from the C-terminal of a precursor protein. These proteins interact with a conserved family of cell surface serine/threonine-specific protein kinase receptors, and generate intracellular signals using a conserved family of proteins called SMADs. They play fundamental roles in the regulation of basic biological processes such as growth, development, tissue homeostasis and regulation of the immune system.
  
  ## Structure
  
  Proteins from the TGF-beta superfamily are only active as homo- or heterodimer; the two chains being linked by a single disulfide bond. From X-ray studies of TGF-beta-2, it is known that all the other cysteines are involved in intrachain disulfide bonds. As shown in the following schematic representation, there are four disulfide bonds in the TGF-beta's and in inhibin beta chains, while the other members of this superfamily lack the first bond.
  
  where 'C' denotes a conserved cysteine involved in a disulfide bond.
  
  ## Examples
  
  Human genes encoding proteins that contain this domain include:
  
  AMH; ARTN; BMP2; BMP3; BMP4; BMP5; BMP6; BMP7; BMP8A; BMP8B; BMP10; BMP15;
  
  GDF1; GDF2; GDF3; GDF5; GDF6; GDF7; GDF9; GDF10; GDF11; GDF15; GDNF; INHA; INHBA; INHBB; INHBC; INHBE; LEFTY1; LEFTY2; MSTN; NODAL; NRTN; PSPN; TGFB1; TGFB2; TGFB3;
  
  