The insulin-like growth factor-binding protein (IGFBP) serves as a
transport protein
A transport protein (variously referred to as a transmembrane pump, transporter, escort protein, acid transport protein, cation transport protein, or anion transport protein) is a protein that serves the function of moving other materials within ...
for
insulin-like growth factor 1
Insulin-like growth factor 1 (IGF-1), also called somatomedin C, is a hormone similar in molecular structure to insulin which plays an important role in childhood growth, and has anabolic effects in adults.
IGF-1 is a protein that in humans ...
(IGF-1).
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.
The IGFBPs help to lengthen the half-life of circulating IGFs in all tissues, including the prostate.
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.
These structural differences can have a tremendous impact on how the IGFBPs interact with cellular basement membranes.
Family members
In humans, IGFBPs are transcribed from the following seven genes:
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IGFBP1
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IGFBP2
Insulin-like growth factor-binding protein 2 is a protein that in humans is encoded by the ''IGFBP2'' gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." mean ...
*
IGFBP3
Insulin-like growth factor-binding protein 3, also known as IGFBP-3, is a protein that in humans is encoded by the ''IGFBP3'' gene. IGFBP-3 is one of six IGF binding proteins ( IGFBP-1 to IGFBP-6) that have highly conserved structures and bind th ...
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IGFBP4
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IGFBP5
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IGFBP6
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IGFBP7
See also
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Insulin-like growth factor receptor
The insulin-like growth factor receptors (IGFRs) include the following two receptors:
* Insulin-like growth factor 1 receptor (IGF-1R)
* Insulin-like growth factor 2 receptor (IGF-2R)
See also
* Insulin-like growth factor
* Insulin-like growth f ...
References
External links
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{{Growth factor receptor modulators
Protein domains
Water-soluble transporters