Catalytic domain of the Protein Tyrosine Kinase, Focal Adhesion Kinase
PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. FAK is a cytoplasmic (or nonreceptor) PTK that contains an autophosphorylation site and a FERM domain at the N-terminus, a central tyr kinase domain, proline-rich regions, and a C-terminal FAT (focal adhesion targeting) domain. FAK activity is dependent on integrin-mediated cell adhesion, which facilitates N-terminal autophosphorylation. Full activation is achieved by the phosphorylation of its two adjacent A-loop tyrosines. FAK is important in mediating signaling initiated at sites of cell adhesions and at growth factor receptors. Through diverse molecular interactions, FAK functions as a biosensor or integrator to control cell motility. It is a key regulator of cell survival, proliferation, migration and invasion, and thus plays an important role in the development and progression of cancer. Src binds to autophosphorylated FAK forming the FAK-Src dual kinase complex, which is activated in a wide variety of tumor cells and generates signals promoting growth and metastasis. FAK is being developed as a target for cancer therapy. The FAK 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.