PMID:14594807
| Citation |
Wolfe, MD, Ahmed, F, Lacourciere, GM, Lauhon, CT, Stadtman, TC and Larson, TJ (2004) Functional diversity of the rhodanese homology domain: the Escherichia coli ybbB gene encodes a selenophosphate-dependent tRNA 2-selenouridine synthase. J. Biol. Chem. 279:1801-9 |
|---|---|
| Abstract |
Escherichia coli has eight genes predicted to encode sulfurtransferases having the active site consensus sequence Cys-Xaa-Xaa-Gly. One of these genes, ybbB, is frequently found within bacterial operons that contain selD, the selenophosphate synthetase gene, suggesting a role in selenium metabolism. We show that ybbB is required in vivo for the specific substitution of selenium for sulfur in 2-thiouridine residues in E. coli tRNA. This modified tRNA nucleoside, 5-methylaminomethyl-2-selenouridine (mnm(5)se(2)U), is located at the wobble position of the anticodons of tRNA(Lys), tRNA(Glu), and tRNA(1)(Gln). Nucleoside analysis of tRNAs from wild-type and ybbB mutant strains revealed that production of mnm(5)se(2)U is lost in the ybbB mutant but that 5-methylaminomethyl-2-thiouridine, the mnm(5)se(2)U precursor, is unaffected by deletion of ybbB. Thus, ybbB is not required for the initial sulfurtransferase reaction but rather encodes a 2-selenouridine synthase that replaces a sulfur atom in 2-thiouridine in tRNA with selenium. Purified 2-selenouridine synthase containing a C-terminal His(6) tag exhibited spectral properties consistent with tRNA bound to the enzyme. In vitro mnm(5)se(2)U synthesis is shown to be dependent on 2-selenouridine synthase, SePO(3), and tRNA. Finally, we demonstrate that the conserved Cys(97) (but not Cys(96)) in the rhodanese sequence motif Cys(96)-Cys(97)-Xaa-Xaa-Gly is required for 2-selenouridine synthase in vivo activity. These data are consistent with the ybbB gene encoding a tRNA 2-selenouridine synthase and identifies a new role for the rhodanese homology domain in enzymes. |
| Links |
PubMed Online version:10.1074/jbc.M310442200 |
| Keywords |
Amino Acid Sequence; Binding Sites; Cloning, Molecular; Escherichia coli/enzymology; Escherichia coli Proteins/chemistry; Molecular Sequence Data; Phosphates/physiology; Selenium/metabolism; Selenium Compounds; Sulfurtransferases/chemistry; Sulfurtransferases/genetics; Sulfurtransferases/physiology; Thiosulfate Sulfurtransferase/chemistry; Thiosulfate Sulfurtransferase/physiology |
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