Queuine

Queuine (Q) is a hypermodified nucleobase found in the first (or wobble) position of the anticodon of tRNAs specific for Asn, Asp, His, and Tyr, in most eukaryotes and prokaryotes.

The nucleoside of queuine is queuosine. Queuine is not found in the tRNA of archaea; however, a related 7-deazaguanine derivative, the nucleoside of which is archaeosine, occurs in different tRNA position, the dihydrouridine loop, and in tRNAs with more specificities.