Insulin-like growth factor-binding protein
{{short description|Transport protein for insulin-like growth factor 1}}
{{Pfam_box
| Symbol = IGFBP
| Name = Insulin-like growth factor
binding protein
| image = PDB 1boe EBI.jpg
| width =
| caption = Structure of the IGF-binding domain of the insulin-like growth factor-binding protein-5 (IGFBP-5){{cite journal |vauthors=Kalus W, Zweckstetter M, Renner C, etal |title=Structure of the IGF-binding domain of the insulin-like growth factor-binding protein-5 (IGFBP-5): implications for IGF and IGF-I receptor interactions |journal=EMBO J. |volume=17 |issue=22 |pages=6558–72 |date=November 1998 |pmid=9822601 |pmc=1171003 |doi=10.1093/emboj/17.22.6558 |url=http://pubman.mpdl.mpg.de/pubman/item/escidoc:2353534/component/escidoc:2353536/2353534.pdf}}
| Pfam = PF00219
| InterPro = IPR000867
| SMART = SM00121
| PROSITE = PDOC00194
| SCOP = 1boe
| TCDB =
| OPM family =
| OPM protein =
| PDB = {{PDB2|1boe}}, {{PDB2|1h59}}
}}
The insulin-like growth factor-binding protein (IGFBP) serves as a transport protein for insulin-like growth factor 1 (IGF-1).{{cite journal |vauthors=Hwa V, Oh Y, Rosenfeld RG | title = The insulin-like growth factor-binding protein (IGFBP) superfamily | journal = Endocr. Rev. | volume = 20 | issue = 6 | pages = 761–87 |date=December 1999 | doi = 10.1210/edrv.20.6.0382 | pmid = 10605625 | doi-access = free }}
Function
Approximately 98% of IGF-1 is always bound to one of six binding proteins (IGF-BP). IGFBP-3, the most abundant protein, accounts for 80% of all IGF binding. IGF-1 binds to IGFBP-3 in a 1:1 molar ratio. IGF-BP also binds to IGF-1 inside the liver, allowing growth hormone to continuously act upon the liver to produce more IGF-1.
IGF binding proteins (IGFBPs) are proteins of 24 to 45 kDa. All six IGFBPs share 50% homology with each other and have binding affinities for IGF-I and IGF-II at the same order of magnitude as the ligands have for the IGF-IR.{{cite journal |vauthors=Clemmons DR, Busby WH, Arai T, Nam TJ, Clarke JB, Jones JI, Ankrapp DK | title = Role of insulin-like growth factor binding proteins in the control of IGF actions | journal = Prog. Growth Factor Res. | volume = 6 | issue = 2–4 | pages = 357–66 | year = 1995 | pmid = 8817679 | doi = 10.1016/0955-2235(95)00013-5}}
The IGFBPs help to lengthen the half-life of circulating IGFs in all tissues, including the prostate.{{cite journal |vauthors=Stewart CE, Bates PC, Calder TA, Woodall SM, Pell JM | title = Potentiation of insulin-like growth factor-I (IGF-I) activity by an antibody: supportive evidence for enhancement of IGF-I bioavailability in vivo by IGF binding proteins | journal = Endocrinology | volume = 133 | issue = 3 | pages = 1462–5 |date=September 1993 | pmid = 7689959 | doi = 10.1210/endo.133.3.7689959}} Individual IGFBPs may act to enhance or attenuate IGF signaling depending on their physiological context (i.e. cell type). Even with these similarities, some characteristics are different: chromosomal location, heparin binding domains, RGD recognition site, preference for binding IGF-I or IGF-II, and glycosylation and phosphorylation differences.{{cite journal |vauthors=Gregory CW, DeGeorges A, Sikes RA | title = The IGF axis in the development and progression of prostate cancer | journal = Recent Research Developments in Cancer | pages = 437–462 | year = 2001 | isbn = 81-7895-002-2}} These structural differences can have a tremendous impact on how the IGFBPs interact with cellular basement membranes.
Family members
See also
References
{{Reflist}}
External links
- {{MeshName|Insulin-like+growth+factor+binding+proteins}}
{{Carrier proteins}}
{{Growth factor receptor modulators}}