Kinase Family TGM
Kinase Classification: Group SAPPK: Family TGM
Tissue Transglutaminase 2 (TGM2) is a multi-functional protein that has been reported in human to phosphorylate several proteins, including p53, Histones and Rb. Its other functions include cross linking of proteins via Glu and Lys residues, acting as a GPCR and possibly as a protein disulfide isomerase.
Evidence for Kinase Activity
TGM2 was first identified as a protein kinase by purification of an IGFBP3 kinase activity from membrane fractions of a cell line [1]. Affinity purification of TGM2 from human, guinea pig or bacculovirus-driven insect expression all had IGFBP3 kinase activity. Inhibitors of the cross-linking activity of TGM2 (cystamine and monodansyl cadaverine) inhibited the kinase activity. Phopshorylation was on Ser and Thr. The immunopurification method used leaves open the possibility that the kinase activity was due to a tightly bound co-purifying protein. High-thoughput protein interaction mapping has shown several kinases among the 94 proteins that associate with TGM2, including PAK1 and PAK2, DLK and RSK2.
The same group showed that immunopurified TGM2 could also phosphorylate as well as cross-link several histones [2], using insect-produced protein. This paper reports (but does not show) that the kinase activity is also seen in E. coli-produced protein and that the kinase activity migrates along with TGM2 in an in-gel kinase activity, decreasing the likelihood that the kinase activity is a contaminant. TGM2 was also seen to phosphorylate p53 on Ser [3], and to phosphorylate Rb protein [4]. Phosphorylation of TGM2 by PKA increased its kinase activity but reduced its transamidating activity.
TGM2 was previously reported to bind hydrolyze both GTP and ATP [5], and this activity was mapped to the first 185 AA, consisting of the Transglutaminase_N domain and about 65 more AA. However, a crystal structure shows GTP binding between the core domain and the C terminus [6], and another report indicates that both ATP and GTP hydrolysis occur in the core domain [7]
Domain Structure
TGM2 has four major conserved regions: A Transglutaminase_N domain of about 120 AA followed by a transgluaminase core region in the middle, and two Transglutaminase_C domains at the C terminus. TGM4 and TGM7 lack the second Transglutaminase_C domain. The core region is similar to that of cysteine proteases and is thought to carry out the transglutaminase reaction, while the N and C terminal domains are related to Ig and Fn3 beta barrel folds, but not to other known enzymes.
Evolution
Human paralogs of TGM2 are TGM1 (TGK), TGM3 (TGE), TGM4, TGM5, TGM6 (TGY), TGM7 (TGMZ), Band 4.2 protein (EPB42), and coagulation factor XIII A (F13A1). F13A1 has been claimed to also have protein kinase activity, though no data was shown [3].
Homologs of the full-length protein are found throughout the metazoa, and the transglutaminase core region is found in some bacteria and archaea, but not in protists or plants.
References
- Mishra S and Murphy LJ. Tissue transglutaminase has intrinsic kinase activity: identification of transglutaminase 2 as an insulin-like growth factor-binding protein-3 kinase. J Biol Chem. 2004 Jun 4;279(23):23863-8. DOI:10.1074/jbc.M311919200 |
- Mishra S, Saleh A, Espino PS, Davie JR, and Murphy LJ. Phosphorylation of histones by tissue transglutaminase. J Biol Chem. 2006 Mar 3;281(9):5532-8. DOI:10.1074/jbc.M506864200 |
- Mishra S and Murphy LJ. The p53 oncoprotein is a substrate for tissue transglutaminase kinase activity. Biochem Biophys Res Commun. 2006 Jan 13;339(2):726-30. DOI:10.1016/j.bbrc.2005.11.071 |
- Mishra S, Melino G, and Murphy LJ. Transglutaminase 2 kinase activity facilitates protein kinase A-induced phosphorylation of retinoblastoma protein. J Biol Chem. 2007 Jun 22;282(25):18108-18115. DOI:10.1074/jbc.M607413200 |
- Lai TS, Slaughter TF, Koropchak CM, Haroon ZA, and Greenberg CS. C-terminal deletion of human tissue transglutaminase enhances magnesium-dependent GTP/ATPase activity. J Biol Chem. 1996 Dec 6;271(49):31191-5. DOI:10.1074/jbc.271.49.31191 |
- Liu S, Cerione RA, and Clardy J. Structural basis for the guanine nucleotide-binding activity of tissue transglutaminase and its regulation of transamidation activity. Proc Natl Acad Sci U S A. 2002 Mar 5;99(5):2743-7. DOI:10.1073/pnas.042454899 |
- Iismaa SE, Chung L, Wu MJ, Teller DC, Yee VC, and Graham RM. The core domain of the tissue transglutaminase Gh hydrolyzes GTP and ATP. Biochemistry. 1997 Sep 30;36(39):11655-64. DOI:10.1021/bi970545e |
