Transfers and isomerizes the ribose moiety from AdoMet to the 7-aminomethyl group of 7-deazaguanine (preQ1-tRNA) to give epoxyqueuosine (oQ-tRNA). 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. Belongs to the QueA family.