Catalytic domain of the Serine/Threonine Kinase, PCTAIRE-1 kinase
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. PCTAIRE-1 is expressed ubiquitously and is localized in the cytoplasm. Its kinase activity is cell cycle dependent and peaks at the S and G2 phases. PCTAIRE-1 is highly expressed in the brain and may play a role in regulating neurite outgrowth. It can also associate with Trap (Tudor repeat associator with PCTAIRE-2), a physiological partner of PCTAIRE-2; with p11, a small dimeric protein with similarity to S100; and with 14-3-3 proteins, mediators of phosphorylation-dependent interactions in many different proteins. PCTAIRE-1 shares sequence similarity with Cyclin-Dependent Kinases (CDKs), which belong to a large family of STKs that are regulated by their cognate cyclins. Together, CDKs and cyclins are involved in the control of cell-cycle progression, transcription, and neuronal function. The PCTAIRE-1 subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.