Human IR

The Insulin Receptor (gene name INSR, designated CD220) is a type I transmembrane glycoprotein in the Insulin/IGF Receptor family of receptor tyrosine kinases that share structural similarity and overlapping intracellular signaling events. The 1382 amino acid (aa) human Insulin R preproprotein (B isoform) is processed by proteolysis to remove the signal peptide and produce an extracellular alpha portion (aa 28-762), and an extracellular/transmembrane/cytoplasmic beta subunit (aa 763-1382). The extracellular domain (ECD) contains two homologous globular domains separated by a cysteine-rich domain and followed by three fibronectin type III domains. The intracellular region contains insulin-receptor substrate (IRS) docking sites, the kinase domain, and a phosphotyrosine-containing linker region.) IR-A expression is highest in fetal tissues and cancer cells, while IR-B is concentrated in adult differentiated cells (1-5).