Queuosine (Q) biosynthesis protein, or S-adenosylmethionine:tRNA -ribosyltransferase-isomerase, is required for the synthesis of the queuosine precursor (oQ). It catalyses the transfer and isomerisation of the ribose moiety from AdoMet to the 7-aminomethyl group of 7-deazaguanine (preQ1-tRNA) to form epoxyqueuosine (oQ-tRNA). Q is a hypermodified nucleoside usually found at the first position of the anticodon of asparagine, aspartate, histidine, and tyrosine tRNAs [1,2]. In Streptococcus gordonii , QueA has been shown to play a role in the regulation of arginine deiminase genes [3].

1: A new function of S-adenosylmethionine: the ribosyl moiety of AdoMet is the precursor of the cyclopentenediol moiety of the tRNA wobble base queuine. Slany RK, Bosl M, Crain PF, Kersten H; Biochemistry 1993;32:7811-7817. PMID:8347586

2: Kinetic mechanism of the tRNA-modifying enzyme S-adenosylmethionine:tRNA ribosyltransferase-isomerase (QueA). Van Lanen SG, Iwata-Reuyl D; Biochemistry. 2003;42:5312-5320. PMID:12731872

3: Environmental and growth phase regulation of the Streptococcus gordonii arginine\tdeiminase genes. Liu Y, Dong Y, Chen YY, Burne RA; Appl Environ Microbiol. 2008;74:5023-5030. PMID:18552185