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Catalytic domain of the Protein Tyrosine Kinase, Fibroblast Growth Factor Receptor 1 PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. Alternative splicing of FGFR1 transcripts produces a variety of isoforms, which are differentially expressed in cells. FGFR1 binds the ligands, FGF1 and FGF2, with high affinity and has also been reported to bind FGF4, FGF6, and FGF9. FGFR1 signaling is critical in the control of cell migration during embryo development. It promotes cell proliferation in fibroblasts. Nuclear FGFR1 plays a role in the regulation of transcription. Mutations, insertions or deletions of FGFR1 have been identified in patients with Kallman's syndrome (KS), an inherited disorder characterized by hypogonadotropic hypogonadism and loss of olfaction. Aberrant FGFR1 expression has been found in some human cancers including 8P11 myeloproliferative syndrome (EMS), breast cancer, and pancreatic adenocarcinoma. FGFR1 is part of the FGFR subfamily, which are receptor PTKs (RTKs) containing an extracellular ligand-binding region with three immunoglobulin-like domains, a transmembrane segment, and an intracellular catalytic domain. The binding of FGFRs to their ligands, the FGFs, results in receptor dimerization and activation, and intracellular signaling. The binding of FGFs to FGFRs is promiscuous, in that a receptor may be activated by several ligands and a ligand may bind to more that one type of receptor. The FGFR1 subfamily is part of a larger superfamily that includes the catalytic domains of other kinases such as protein serine/threonine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
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