Biochemical and Spectroscopic Studies of Epoxyqueuosine Reductase: A Novel Iron-Sulfur Cluster- and Cobalamin-Containing Protein Involved in the Biosynthesis of Queuosine.
Biochemistry
; 54(31): 4927-35, 2015 Aug 11.
Article
in En
| MEDLINE
| ID: mdl-26230193
ABSTRACT
Queuosine is a hypermodified nucleoside present in the wobble position of tRNAs with a 5'-GUN-3' sequence in their anticodon (His, Asp, Asn, and Tyr). The 7-deazapurine core of the base is synthesized de novo in prokaryotes from guanosine 5'-triphosphate in a series of eight sequential enzymatic transformations, the final three occurring on tRNA. Epoxyqueuosine reductase (QueG) catalyzes the final step in the pathway, which entails the two-electron reduction of epoxyqueuosine to form queuosine. Biochemical analyses reveal that this enzyme requires cobalamin and two [4Fe-4S] clusters for catalysis. Spectroscopic studies show that the cobalamin appears to bind in a base-off conformation, whereby the dimethylbenzimidazole moiety of the cofactor is removed from the coordination sphere of the cobalt but not replaced by an imidazole side chain, which is a hallmark of many cobalamin-dependent enzymes. The bioinformatically identified residues are shown to have a role in modulating the primary coordination sphere of cobalamin. These studies provide the first demonstration of the cofactor requirements for QueG.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Oxidoreductases
/
Bacillus subtilis
/
Bacterial Proteins
/
Vitamin B 12
/
Iron-Sulfur Proteins
/
Nucleoside Q
Language:
En
Journal:
Biochemistry
Year:
2015
Document type:
Article
Affiliation country:
United States