This superfamily includes the Archaeosine tRNA-guanine transglycosylase (ArcTGT), domain C2. The ArcTGT structure consists of the N-terminal catalytic domain (residues 6-360) and the C-terminal region with unidentified functions (residues 361-582) (Figure 3). The C-terminal region is divided into three domains, C1, C2, and C3. This entry represents domain C2 which is formed by a four-stranded antiparallel beta-sheet lined with two alpha-helices. It has conserved basic residues on the surface of the beta-sheets as does the C-terminal domain PUA (INTERPRO:IPR002478, PFAM:PF01472). The catalytic domain of TGT has conserved basic residues on the outer surface of the N-terminal three-stranded beta sheet, which closes the barrel. It is postulated that these basic residues from the three domains form a continuous, positively charged patch to which the tRNA binds PMID:12054814.

PFAM:PF14810, INTERPRO:IPR029402,DOI:10.1016/S0022-2836(02)00090-6