Catalytic domain of the Protein Tyrosine Kinase, Activated Cdc42-associated kinase
PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. This subfamily includes Ack1, thirty-eight-negative kinase 1 (Tnk1), and similar proteins. They are cytoplasmic (or nonreceptor) PTKs containing an N-terminal catalytic domain, an SH3 domain, a Cdc42-binding CRIB domain, and a proline-rich region. They are mainly expressed in brain and skeletal tissues and are involved in the regulation of cell adhesion and growth, receptor degradation, and axonal guidance. Ack1 is also associated with androgen-independent prostate cancer progression. Tnk1 regulates TNFalpha signaling and may play an important role in cell death. The Ack-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.