Catalytic domain of the Serine/Threonine kinase, Mitogen-activated protein kinase-activated protein kinase 3
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. MAPK-activated protein kinase 3 (MAPKAP3 or MK3) contains an N-terminal proline-rich region that can bind to SH3 domains, a catalytic kinase domain followed by a C-terminal autoinhibitory region that contains nuclear localization (NLS) and nuclear export (NES) signals with a p38 MAPK docking motif that overlaps the NLS. MK3 is a bonafide substrate for the MAPK p38. It is closely related to MK2 and thus far, MK2/3 show indistinguishable substrate specificity. They are mainly involved in the regulation of gene expression and they participate in diverse cellular processes such as endocytosis, cytokine production, cytoskeletal reorganization, cell migration, cell cycle control and chromatin remodeling. They are implicated in inflammation and cance and their substrates include mRNA-AU-rich-element (ARE)-binding proteins (TTP and hnRNP A0), Hsp proteins (Hsp27 and Hsp25) and RSK, among others. MK2/3 are both expressed ubiquitously but MK2 is expressed at significantly higher levels. MK3 activity is only significant when MK2 is absent. The MK3 subfamily is part of a larger superfamily that includes the catalytic domains of other protein 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.",