Competitive Binding of Magnesium to Calcium Binding Sites Reciprocally Regulates Transamidase and GTP Hydrolysis Activity of Transglutaminase 2

Abstract

Transglutaminase 2 (TG2) is a Ca 2+ -dependent enzyme, which regulates various cellular processes by catalyzing protein crosslinking or polyamination. Intracellular TG2 is activated and inhibited by Ca 2+ and GTP binding, respectively. Although aberrant TG2 activation has been implicated in the pathogenesis of diverse diseases, including cancer and degenerative and fibrotic diseases, the structural basis for the regulation of TG2 by Ca 2+ and GTP binding is not fully understood.Here, we produced and analyzed a Ca 2+ -containing TG2 crystal, and identified two glutamate residues, E437 and E539, as Ca 2+ -binding sites. The enzymatic analysis of the mutants revealed that Ca 2+ binding to these sites is required for the transamidase activity of TG2. Interestingly, we found that magnesium (Mg 2+ ) competitively binds to the E437 and E539 residues. The Mg 2+ binding to these allosteric sites enhances the GTP binding/hydrolysis activity but inhibits transamidase activity. Furthermore, HEK293 cells transfected with mutant TG2 exhibited higher transamidase activity than cells with wild-type TG2. Cells with wild-type TG2 showed an increase in transamidase activity under Mg 2+ -depleted conditions, whereas cells with mutant TG2 were unaffected. These results indicate that E437 and E539 are Ca 2+ -binding sites contributing to the reciprocal regulation of transamidase and GTP binding/hydrolysis activities of TG2 through competitive Mg 2+ binding.

Proteomic profiling of epicardial fat in heart failure with preserved versus reduced and mildly reduced ejection fraction

“…The consistency of TGM2 down‐regulated in EAT and plasma level indicate that TGM2 as a potential molecule plays an important role in HFrEF/HFmrEF patients. TGM2 is a calcium‐dependent acyltransferase which catalyses the formation of covalent bonds between peptide‐bound glutamine and various other amines, such as gamma‐amino group of peptide‐bound lysine, or mono‐and polyamines, thereby implicating the cross‐linking of proteins such as ACO2, HSPB6, FN1, HMGB1, RAP1GDS1, SPP1 24,25 and the conjugation of polyamines to proteins 26,27 . It involves in many biological processes, such as chromatin modification and apoptosis, cellular differentiation, angiogenesis, bone development and wound healing 28 .…”

“…TGM2 is a calcium-dependent acyltransferase which catalyses the formation of covalent bonds between peptide-bound glutamine and various other amines, such as gamma-amino group of peptide-bound lysine, or mono-and polyamines, thereby implicating the crosslinking of proteins such as ACO2, HSPB6, FN1, HMGB1, RAP1GDS1, SPP1 24,25 and the conjugation of polyamines to proteins. 26,27 It involves in many biological processes, such as chromatin modification and apoptosis, cellular differentiation, angiogenesis, bone development and wound healing. 28 Under physiological conditions, the protein cross-linking activity is inhibited by GTP, but the inhibition is relieved by Ca 2+ in response to various stresses.…”

Chemical and Pasting Properties of Potato Flour (Solanum tuberosum L.) in relation to Different Processing Techniques

“…This can lead to a higher peak viscosity, breakdown viscosity, and final viscosity [63]. Magnesium ions, on the other hand, can weaken the gel network by competing with calcium binding sites on the starch molecules [64]. Consequently, peak viscosity may be lower, and setback viscosity may be higher.…”

Structures of Human Transglutaminase 2: Finding Clues for Interference in Cross-linking Mediated Activity

“…Ca 2+ was initially assumed to promote the structural transition of TGase2 to its active form. A recent study, however, showed that Ca 2+ binding to TGase2 did not lead to a dramatic structural transition [65]. In contrast, nucleotides such as GTP, GDP (guanosine diphosphate), and ATP (adenosine triphosphate) are well-known inhibitors of the transamidation activity of TGase2 [66].…”