Non-catalytic subunit of the queuine tRNA-ribosyltransferase (TGT) that catalyzes the base-exchange of a guanine (G) residue with queuine (Q) at position 34 (anticodon wobble position) in tRNAs with GU(N) anticodons (tRNA-Asp, -Asn, -His and -Tyr), resulting in the hypermodified nucleoside queuosine (7-(((4,5-cis-dihydroxy-2-cyclopenten-1-yl)amino)methyl)-7-deazaguanosine). Binds 1 zinc ion per subunit. Heterodimer of a catalytic subunit QTRT1 and an accessory subunit QTRT2. May associate with the mitochondrion outer membrane. Expressed in brain, heart, kidney, liver, lung, skeletal muscle, spleen and testis. Major isoform in adult tissues. Belongs to the queuine tRNA-ribosyltransferase family. QTRT2 subfamily.