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Catalytic domain of the Protein Tyrosine Kinase, Epidermal Growth Factor Receptor PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. EGFR (HER1, ErbB1) is a receptor PTK (RTK) containing an extracellular EGF-related ligand-binding region, a transmembrane helix, and a cytoplasmic region with a tyr kinase domain and a regulatory C-terminal tail. Unlike other PTKs, phosphorylation of the activation loop of EGFR proteins is not critical to their activation. Instead, they are activated by ligand-induced dimerization, leading to the phosphorylation of tyr residues in the C-terminal tail, which serve as binding sites for downstream signaling molecules. Ligands for EGFR include EGF, heparin binding EGF-like growth factor (HBEGF), epiregulin, amphiregulin, TGFalpha, and betacellulin. Upon ligand binding, EGFR can form homo- or heterodimers with other EGFR subfamily members. The EGFR signaling pathway is one of the most important pathways regulating cell proliferation, differentiation, survival, and growth. Overexpression and mutation in the kinase domain of EGFR have been implicated in the development and progression of a variety of cancers. A number of monoclonal antibodies and small molecule inhibitors have been developed that target EGFR, including the antibodies Cetuximab and Panitumumab, which are used in combination with other therapies for the treatment of colorectal cancer and non-small cell lung carcinoma (NSCLC). The small molecule inhibitors Gefitinib (Iressa) and Erlotinib (Tarceva), already used for NSCLC, are undergoing clinical trials for other types of cancer including gastrointestinal, breast, head and neck, and bladder. The EGFR 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. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",