C-terminal catalytic domain of the Serine/Threonine Kinase, Ribosomal S6 kinase 2 (also called 90kDa ribosomal protein S6 kinase 3 or Ribosomal protein S6 kinase alpha-3)
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. RSK2 is also called p90RSK3, RPS6KA3, S6K-alpha-3, or MAPK-activated protein kinase 1b (MAPKAPK-1b). RSK2 is expressed highly in the regions of the brain with high synaptic activity. It plays a role in the maintenance and consolidation of excitatory synapses. It is a specific modulator of phospholipase D in calcium-regulated exocytosis. Mutations in the RSK2 gene, RPS6KA3, cause Coffin-Lowry syndrome (CLS), a rare syndromic form of X-linked mental retardation characterized by growth and psychomotor retardation and skeletal abnormalities. RSK2 is one of four RSK isoforms (RSK1-4) from distinct genes present in vertebrates. RSKs contain an N-terminal kinase domain (NTD) from the AGC family and a C-terminal kinase domain (CTD) from the CAMK family. They are activated by signaling inputs from extracellular regulated kinase (ERK) and phosphoinositide dependent kinase 1 (PDK1). ERK phosphorylates and activates the CTD of RSK, serving as a docking site for PDK1, which phosphorylates and activates the NTD, which in turn phosphorylates all known RSK substrates. RSKs act as downstream effectors of mitogen-activated protein kinase (MAPK) and play key roles in mitogen-activated cell growth, differentiation, and survival. The RSK2 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.
Jiyao W et al.(2023). "The conserved domain database in 2023.",