?
 
Catalytic domain of the Serine/Threonine Kinase, Serine-aRginine Protein Kinase STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. SRPKs phosphorylate and regulate splicing factors from the SR protein family by specifically phosphorylating multiple serine residues residing in SR/RS dipeptide motifs (also known as RS domains). Phosphorylation of the RS domains enhances interaction with transportin SR and facilitates entry of the SR proteins into the nucleus. SRPKs contain a nonconserved insert domain, within the well-conserved catalytic kinase domain, that regulates their subcellular localization. They play important roles in mediating pre-mRNA processing and mRNA maturation, as well as other cellular functions such as chromatin reorganization, cell cycle and p53 regulation, and metabolic signaling. Vertebrates contain three distinct SRPKs, called SRPK1-3. The SRPK homolog in budding yeast, Sky1p, recognizes and phosphorylates its substrate Npl3p, which lacks a classic RS domain but contains a single RS dipeptide at the C-terminus of its RGG domain. Npl3p is a shuttling heterogeneous nuclear ribonucleoprotein (hnRNP) that exports a distinct class of mRNA from the nucleus to the cytoplasm. The SRPK 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.",