Transfers and isomerizes the ribose moiety from AdoMet to the 7-aminomethyl group of 7-deazaguanine (preQ1-tRNA) to give epoxyqueuosine (oQ-tRNA) (By similarity). Seems to have a role in modulation of ADS (arginine deiminase system) gene expression, perhaps exerting a negative effect on the translation of arc regulatory proteins. 7-aminomethyl-7-carbaguanosine(34) in tRNA + S-adenosyl-L-methionine = adenine + epoxyqueuosine(34) in tRNA + H(+) + L-methionine tRNA modification; tRNA-queuosine biosynthesis. Monomer. Is constitutively expressed in the different growth phases. Its transcription is not subject to carbon catabolite repression (CCR), and is not affected by arginine or low pH. Is cotranscribed with arcR. The arcA transcript in QueA-deficient strains is 14-fold more abundant than in the wild-type strain. However, no significant difference in arginine deiminase (AD) activity (encoded by arcA) is detected between the wild-type and QueA-deficient strains. The growth rate of a QueA-deficient strain does not differ significantly from that of the wild-type strain, but the QueA-deficient strain does not compete well with the wild-type during serial passage. Belongs to the QueA family.