Spectroscopic and Computational Investigation of the Epoxyqueuosine Reductase QueG Reveals Intriguing Similarities with the Reductive Dehalogenase PceA.

ABSTRACT: Queuosine (Q) is a highly modified nucleoside of transfer RNA that is formed from guanosine triphosphate over the course of eight steps. The final step in this process, involving the conversion of epoxyqueuosine (oQ) to Q, is catalyzed by the enzyme QueG. A recent X-ray crystallographic study revealed that QueG possesses the same cofactors as reductive dehalogenases, including a base-off Co(II)cobalamin (Co(II)Cbl) species and two [4Fe-4S] clusters. While the initial step in the catalytic cycle of QueG likely involves the formation of a reduced Co(I)Cbl species, the mechanisms employed by this enzyme to accomplish the thermodynamically challenging reduction of base-off Co(II)Cbl to Co(I)Cbl and to convert oQ to Q remain unknown. In this study, we have used electron paramagnetic resonance (

SUBMITTER: Greenhalgh ED 

PROVIDER: S-EPMC8935625 | biostudies-literature | 2022 Feb

REPOSITORIES: biostudies-literature