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Catalytic Domain of the Protein Tyrosine Kinase, Mer PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. Mer (or Mertk) is named after its original reported expression pattern (monocytes, epithelial, and reproductive tissues). It is required for the ingestion of apoptotic cells by phagocytes such as macrophages, retinal pigment epithelial cells, and dendritic cells. Mer is also important in maintaining immune homeostasis. Mer is a member of the TAM subfamily, composed of receptor PTKs (RTKs) containing an extracellular ligand-binding region with two immunoglobulin-like domains followed by two fibronectin type III repeats, a transmembrane segment, and an intracellular catalytic domain. Binding to their ligands, Gas6 and protein S, leads to receptor dimerization, autophosphorylation, activation, and intracellular signaling. The Mer subfamily is part of a larger superfamily that includes the catalytic domains of other kinases such as serine/threonine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",