Catalytic domain of Discoidin Domain Receptor-like Protein Tyrosine Kinases
PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. DDR-like proteins are members of the DDR subfamily, which are receptor PTKs (RTKs) containing an extracellular discoidin homology domain, a transmembrane segment, an extended juxtamembrane region, and an intracellular catalytic domain. The binding of the ligand, collagen, to DDRs results in a slow but sustained receptor activation. DDRs regulate cell adhesion, proliferation, and extracellular matrix remodeling. They have been linked to a variety of human cancers including breast, colon, ovarian, brain, and lung. There is no evidence showing that DDRs act as transforming oncogenes. They are more likely to play a role in the regulation of tumor growth and metastasis. The DDR-like 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.