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Catalytic domain of the Serine/Threonine protein kinase, Vaccinia Related Kinase STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. VRKs were initially discovered due to its similarity to vaccinia virus B1R STK, which is important for viral replication. They play important roles in cell signaling, nuclear envelope dynamics, apoptosis, and stress responses. Vertebrates contain three VRK proteins (VRK1, VRK2, and VRK3) while invertebrates, specifically fruit flies and nematodes, seem to carry only a single ortholog. Mutations of VRK in Drosophila and Caenorhabditis elegans showed varying phenotypes ranging from embryonic lethality to mitotic and meiotic defects resulting in sterility. In vertebrates, VRK1 is implicated in cell cycle progression and proliferation, nuclear envelope assembly, and chromatin condensation. VRK2 is involved in modulating JNK signaling. VRK3 is an inactive pseudokinase that inhibits ERK signaling. The VRK 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.",