The TGS domain is named after ThrRS, GTPase, and SpoT [1]. Interestingly, TGS domain was detected also at the amino terminus of the uridine kinase from the spirochaete Treponema pallidum (but not any other organism, including the related spirochaete Borrelia burgdorferi). TGS is a small domain that consists of ~50 amino acid residues and is predicted to possess a predominantly beta-sheet structure. There is no direct information on the functions of the TGS domain, but its presence in two types of regulatory proteins (the GTPases and guanosine polyphosphate phosphohydrolases/synthetases) suggests a ligand (most likely nucleotide)-binding, regulatory role [1].

1: Evolution of aminoacyl-tRNA synthetases--analysis of unique domain architectures and phylogenetic trees reveals a complex history of horizontal gene transfer events. Wolf YI, Aravind L, Grishin NV, Koonin EV; Genome Res 1999;9:689-710. PMID:10447505

2: The structure of threonyl-tRNA synthetase-tRNA(Thr) complex enlightens its repressor activity and reveals an essential zinc ion in the active site. Sankaranarayanan R, Dock-Bregeon AC, Romby P, Caillet J, Springer M, Rees B, Ehresmann C, Ehresmann B, Moras D; Cell 1999;97:371-381. PMID:10319817