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Receptor Tyrosine Kinase Biology

Receptor tyrosine kinases (RTKs, protein tyrosine kinases, receptor PTKs) are phosphotransferase enzymes that transfer a phosphate group from ATP to a tyrosine amino acid residue creating ADP and a phosphotyrosine in the protein. Receptor tyrosine kinases mediate transmembrane transduction of extracellular signals to the cytoplasm. These signals control normal cellular processes including cell growth, differentiation, and cell osmotic response, as well as abnormal growth or cancer by feedback up- or down-regulation. There are about 20 classes of RTK, including ErbB, EGFR, FGF, and VEGF receptor families, that are are high-affinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones. About 2/3 of all unique tyrosine kinases are of the receptor type, indicating membrane-spanning cell surface proteins which transmit signals in response to binding of soluble or membrane-anchored small molecules.