Figure 1.

The four domains of transglutaminase 2 (TGase 2), presented with binding domains. The catalytic core domain of TGase 2 is responsible for its enzymatic activity, which is induced by Ca²⁺ (a.a. 430–453). The β-barrel 1 domain of TGase 2 contains a heparin-binding site (a.a. 262–265) [28] and a guanosine tri/diphosphate (GTP/GDP)-binding site (a.a. 476–478 and 538–580) [29,30,31]. The C-terminal β-barrel 2 domain of TGase 2 contains a heparin-binding site (a.a. 598–602) [28] and the dimerization motif (a.a. 593–600) [29]. Together, the combined β-barrel 1 and 2 domains of TGase 2 contain binding sites for p62 (a.a. 460–687) [30] and endostatin (a.a. 460–687) [31]. TGase 2 contains an extracellular trafficking sequence at the N-terminus (a.a. 88–106) of the β-sandwich domain [32]. The TGase 2 quadruple point mutant (Q95A, Q96A, Q103A, R116A) cannot bind GK921 [24].