Kinase Family ITPK
ITPK in an inositol lipid kinase, once thought to have protein kinase activity. ITPK is an Inositol 1, 3, 4-trisphosphate 5/6-kinase.
Kinase Domain
ITPK has an ATP-grasp domain, shared by a variety of ATP-hydrolyzing metabolic enzymes. The PIP5K family of phosphatidyl inositol kinases is weakly related, in having a kinase domain that is related both to ATP-grasp and PKL kinases.
Claimed Protein Kinase Activity
Two report showed protein kinase activity associated with human IPTK1 [1, 2], when moderately purified from human cell culture. The kinase activity could phosphorylate several transcription factors and copurified with the COP9 signalosome complex. However, a later study [3] separated the protein and lipid kinase activities chromatographically, indicating that the original report may have been due to a contaminating protein kinase. Several predicted kinase-dead mutations abolished lipid kinase activity but did not affect the associated protein kinase activity
References
- Sun Y, Wilson MP, and Majerus PW. Inositol 1,3,4-trisphosphate 5/6-kinase associates with the COP9 signalosome by binding to CSN1. J Biol Chem. 2002 Nov 29;277(48):45759-64. DOI:10.1074/jbc.M208709200 |
- Wilson MP, Sun Y, Cao L, and Majerus PW. Inositol 1,3,4-trisphosphate 5/6-kinase is a protein kinase that phosphorylates the transcription factors c-Jun and ATF-2. J Biol Chem. 2001 Nov 2;276(44):40998-1004. DOI:10.1074/jbc.M106605200 |
- Qian X, Mitchell J, Wei SJ, Williams J, Petrovich RM, and Shears SB. The Ins(1,3,4)P3 5/6-kinase/Ins(3,4,5,6)P4 1-kinase is not a protein kinase. Biochem J. 2005 Jul 15;389(Pt 2):389-95. DOI:10.1042/BJ20050297 |
