Catalytic domain of Epidermal Growth Factor Receptor-like Protein Tyrosine Kinases
PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. EGFR (HER, ErbB) subfamily members include EGFR (HER1, ErbB1), HER2 (ErbB2), HER3 (ErbB3), HER4 (ErbB4), and similar proteins. They are receptor PTKs (RTKs) 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, resulting in the phosphorylation of tyr residues in the C-terminal tail, which serve as binding sites for downstream signaling molecules. Collectively, they can recognize a variety of ligands including EGF, TGFalpha, and neuregulins, among others. All four subfamily members can form homo- or heterodimers. HER3 contains an impaired kinase domain and depends on its heterodimerization partner for activation. EGFR subfamily members are involved in signaling pathways leading to a broad range of cellular responses including cell proliferation, differentiation, migration, growth inhibition, and apoptosis. Gain of function alterations, through their overexpression, deletions, or point mutations in their kinase domains, have been implicated in various cancers. These receptors are targets of many small molecule inhibitors and monoclonal antibodies used in cancer therapy. 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.",