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Pseudokinase domain of Vaccinia Related Kinase 3 The pseudokinase domain shows similarity to protein kinases but lacks crucial residues for catalytic activity. 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. VRK3 is an inactive pseudokinase that is unable to bind ATP. It achieves its regulatory function through protein-protein interactions. It negatively regulates ERK signaling by binding directly and enhancing the activity of the MAPK phosphatase VHR (vaccinia H1-related), which dephosphorylates and inactivates ERK. The VRK3 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.
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