InterPro domain: IPR002616

Queuine tRNA-ribosyltransferases, also known as tRNA-guanine transglycosylases (TGT) 2.4.2.29 , modify tRNAs for asparagine, aspartic acid, histidine and tyrosine with queuine at position 34 and with archaeosine at position 15 in archaeal tRNAs. In bacteria it catalyses the exchange of guanine-34 at the wobble position with 7-aminomethyl-7-deazaguanine (preQ1), and subsequently the addition of a cyclopentenediol moiety to 7-aminomethyl-7-deazaguanine-34 tRNA giving a hypermodified base queuine (Q) in the wobble position [ 1 , 2 ]. In eukaryotes, TGT catalyses the irreversible exchange of guanine in the unmodified tRNA with free queuine. Eukaryotes cannot synthesize queuine de novo and must obtain it from the diet or gut flora [ 3 ].

The structure of TGT consists of an irregular (beta/alpha) ₈ barrel, represented by this entry, and a C-terminal zinc-containing subdomain [ 4 ].

1. Crystal structure of tRNA-guanine transglycosylase: RNA modification by base exchange. EMBO J. 15, 2850-7
2. tRNA-guanine transglycosylase from Escherichia coli. Overexpression, purification and quaternary structure. J. Mol. Biol. 231, 489-97
3. Characterization of cDNA encoding the human tRNA-guanine transglycosylase (TGT) catalytic subunit. Gene 265, 205-12