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.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:[3][4][5] Transforming growth factor-beta (TGF-beta)[6] 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.[3] 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,[7] it is known that all the other cysteines are involved in intrachain disulfide bonds.