Catalytic domain of the Serine/Threonine Kinase, p21-activated kinase 5
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. PAK5 is mainly expressed in the brain. It is not required for viability, but together with PAK6, it is required for normal levels of locomotion and activity, and for learning and memory. PAK5 cooperates with Inca (induced in neural crest by AP2) in the regulation of cell adhesion and cytoskeletal organization in the embryo and in neural crest cells during craniofacial development. PAK5 may also play a role in controlling the signaling of Raf-1, an effector of Ras, at the mitochondria. PAK5 belongs to the group II PAKs, which contain a PBD (p21-binding domain) and a C-terminal catalytic domain, but do not harbor an AID (autoinhibitory domain) or SH3 binding sites. PAKs are Rho family GTPase-regulated kinases that serve as important mediators in the function of Cdc42 (cell division cycle 42) and Rac. The PAK 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.