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Structural Basis for the Regulation of Insulin-Like Growth Factors (IGFs) by IGF Binding Proteins (IGFBPs)
Insulin-like growth factor binding proteins (IGFBPs) control the extracellular distribution, function, and activity of IGFs. Here, we report an X-ray structure of the binary complex of IGF-I and the N-terminal domain of IGFBP-4 (NBP-4, residues 3-82) and a model of the ternary complex of IGF-I, NBP-4, and the C-terminal domain (CBP-4, residues 151-232) derived from diffraction data with weak definition of the C-terminal domain. These structures show how the IGFBPs regulate IGF signaling. Key features of the structures include (1) a disulphide bond ladder that binds to IGF and partially masks the IGF residues responsible for type 1 IGF receptor (IGF-IR) binding, (2) the high-affinity IGF-I interaction site formed by residues 39-82 in a globular fold, and (3) CBP-4 interactions. Although CBP-4 does not bind individually to either IGF-I or NBP-4, in the ternary complex, CBP-4 contacts both and also blocks the IGF-IR binding region of IGF-I.
Structural basis for the regulation of insulin-like growth factors by IGF binding proteins., Siwanowicz I, Popowicz GM, Wisniewska M, Huber R, Kuenkele KP, Lang K, Engh RA, Holak TA, Structure. 2005 Jan;13(1):155-67. PMID:15642270
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
[IGF1B_HUMAN] Defects in IGF1 are the cause of insulin-like growth factor I deficiency (IGF1 deficiency) [MIM:608747]. IGF1 deficiency is an autosomal recessive disorder characterized by growth retardation, sensorineural deafness and mental retardation.
[IBP4_HUMAN] IGF-binding proteins prolong the half-life of the IGFs and have been shown to either inhibit or stimulate the growth promoting effects of the IGFs on cell culture. They alter the interaction of IGFs with their cell surface receptors. [IGF1B_HUMAN] The insulin-like growth factors, isolated from plasma, are structurally and functionally related to insulin but have a much higher growth-promoting activity. May be a physiological regulator of [1-14C]-2-deoxy-D-glucose (2DG) transport and glycogen synthesis in osteoblasts. Stimulates glucose transport in rat bone-derived osteoblastic (PyMS) cells and is effective at much lower concentrations than insulin, not only regarding glycogen and DNA synthesis but also with regard to enhancing glucose uptake.
About this Structure
- Siwanowicz I, Popowicz GM, Wisniewska M, Huber R, Kuenkele KP, Lang K, Engh RA, Holak TA. Structural basis for the regulation of insulin-like growth factors by IGF binding proteins. Structure. 2005 Jan;13(1):155-67. PMID:15642270 doi:10.1016/j.str.2004.11.009