Discovery of epoxyqueuosine (oQ) reductase reveals parallels between halorespiration and tRNA modification

Zachary D. Miles, Reid M. McCarty, Gabriella Molnar, Vahe Bandarian

Research output: Contribution to journalArticlepeer-review

71 Scopus citations


Transfer RNA is one of the most richly modified biological molecules. Biosynthetic pathways that introduce these modifications are underexplored, largely because their absence does not lead to obvious phenotypes under normal growth conditions. Queuosine (Q) is a hypermodified base found in the wobble positions of tRNA Asp, Asn, His, and Tyr from bacteria to mankind. Using liquid chromatography MS methods, we have screened 1,755 single gene knockouts of Escherichia coli and have identified the key final step in the biosynthesis of Q. The protein is homologous to B12-dependent iron-sulfur proteins involved in halorespiration. The recombinant Bacillus subtilis epoxyqueuosine (oQ) reductase catalyzes the conversion of oQ to Q in a synthetic substrate, as well as undermodified RNA isolated from an oQ reductase knockout strain. The activity requires inclusion of a reductant and a redox mediator. Finally, exogenously supplied cobalamin stimulates the activity. This work provides the framework for studies of the biosynthesis of other modified RNA components, where lack of accessible phenotype or obvious gene clustering has impeded discovery. Moreover, discovery of the elusive oQ reductase protein completes the biosynthetic pathway of Q.

Original languageEnglish (US)
Pages (from-to)7368-7372
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number18
StatePublished - May 3 2011
Externally publishedYes


  • Biochemistry
  • Queuosine
  • Reductive dehalogenation

ASJC Scopus subject areas

  • General


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