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Catalytic domain of the Protein Tyrosine Kinase, Fes PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. Fes (or Fps) is a cytoplasmic (or nonreceptor) PTK containing an N-terminal region with FCH (Fes/Fer/CIP4 homology) and coiled-coil domains, followed by a SH2 domain, and a C-terminal catalytic domain. The genes for Fes (feline sarcoma) and Fps (Fujinami poultry sarcoma) were first isolated from tumor-causing retroviruses. The viral oncogenes encode chimeric Fes proteins consisting of Gag sequences at the N-termini, resulting in unregulated PTK activity. Fes kinase is expressed in myeloid, vascular endothelial, epithelial, and neuronal cells. It plays important roles in cell growth and differentiation, angiogenesis, inflammation and immunity, and cytoskeletal regulation. A recent study implicates Fes kinase as a tumor suppressor in colorectal cancer. The Fes 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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