Transglutaminase II: a new class of GTP-binding protein with new biological functions

Tissue type transglutaminase (TGase II) is historically a member of the transglutaminase family, which covalently cross-links cellular proteins and polyamines. A recent new finding in the TGase II field is that the enzyme functions as a signal mediator from receptors to an effector in transmembrane signaling. This review will discuss the recent development of TGase II. This new signal transducer was termed Gh when initially discovered and was recently found to be TGase II. To help the reader understand the role of Gh as a signal mediator, the role of heterotrimeric G-proteins in hormone-mediated transmembrane signaling is briefly discussed. We have highlighted how Gh transmits the alpha 1-adrenoceptor signal to the phospholipase C-delta 1 and how Gh is activated and deactivated compared to the prototype of heterotrimeric G-proteins. Recent developments regarding the structure-function of Gh and other biological functions of Gh are discussed to facilitate understanding the impact of Gh in cells.