Involved in specific tRNA modification. Catalyzes the oxygen-dependent hydroxylation of 2-methylthio-N-6-isopentenyl adenosine (ms2i6A) to produce 2-methylthio-N-6-(cis-hydroxy)isopentenyl adenosine (ms2io6A) at position 37 in tRNAs (PubMed:8253666, PubMed:17679698, PubMed:23906247). Can also use N6-(dimethylallyl)adenosine (i6A) as substrate, with lower efficiency (PubMed:23906247, PubMed:25453905). The presence of the hydroxyl group on the tRNA may regulate the ability of S.typhimurium to grow on the citric acid cycle (CAC) intermediates succinate, fumarate and malate (PubMed:9620964). 2-methylsulfanyl-N(6)-dimethylallyladenosine(37) in tRNA + AH2 + O2 = A + H2O + N(6)-[(2E)-4-hydroxy-3-methylbut-2-en-1-yl]-2-(methylsulfanyl)adenosine(37) in tRNA Contains a nonheme dinuclear iron cluster (PubMed:17679698, PubMed:23906247, PubMed:25453905). Contains three different forms of the dinuclear site: an hydroxo-bridged FeIII-OH-FeIII center, an oxo-bridged FeIII-O-FeIII center and an hydroxo-bridged FeII-OH-FeIII mixed-valent center (PubMed:17679698). tRNA modification; 2-methylthio-N-6-(cis-hydroxy)isopentenyl adenosine-tRNA biosynthesis. Monomer. Binding of tRNA to MiaE induces a protein conformational change that influences the electronic structure of the diiron site. Disruption mutant shows normal growth characteristics after being shifted from anaerobic to aerobic conditions (PubMed:8253666). Mutant shows slower growth on citrate and acetate, and is unable to grow on the citric acid cycle intermediates succinate, fumarate and malate (PubMed:8253666, PubMed:9620964). Belongs to the MiaE family. It is uncertain whether Met-1 or Met-17 is the initiator.