This domain of unknown function occurs in Epoxyqueuosine reductase QueG, an iron-sulfur cluster-binding protein, together with the 4Fe-4S binding domain (Pfam:PF00037). QueG catalyses the conversion of epoxyqueuosine (oQ) to queuosine (Q), which is a hypermodified base found in the wobble positions of tRNA(Asp), tRNA(Asn), tRNA(His) and tRNA(Tyr) [1].

1: Discovery of epoxyqueuosine (oQ) reductase reveals parallels between halorespiration and tRNA modification. Miles ZD, McCarty RM, Molnar G, Bandarian V; Proc Natl Acad Sci U S A. 2011;108:7368-7372. PMID:21502530