Human IGF1R

IGF-I receptor is a disulfide-linked heterotetrameric transmembrane protein consisting of two alpha and two beta subunits. Both the alpha and beta subunits are encoded within a single receptor precursor cDNA. The proreceptor polypeptide is proteolytically cleaved and disulfide-linked to yield the mature heterotetrameric receptor. The alpha subunit of IGF-I receptor is extracellular while the beta subunit has an extracellular domain, a transmembrane domain and a cytoplasmic tyrosine kinase domain. The IGF-I receptor is highly expressed in all cell types and tissues. Essentially all of the biological activities of IGF-I and II have been shown to be mediated via IGF-I R (1).