The iscS gene is essential for the biosynthesis of 2-selenouridine in tRNA and the selenocysteine-containing formate dehydrogenase H.
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Mihara H, Kato S, Lacourciere GM, Stadtman TC, Kennedy RA, Kurihara T, Tokumoto U, Takahashi Y, Esaki N
The iscS gene is essential for the biosynthesis of 2-selenouridine in tRNA and the selenocysteine-containing formate dehydrogenase H.
Proc Natl Acad Sci U S A. 2002 May 14;99(10):6679-83. Epub 2002 May 7.
- PubMed ID
- 11997471 [ View in PubMed]
- Abstract
Three NifS-like proteins, IscS, CSD, and CsdB, from Escherichia coli catalyze the removal of sulfur and selenium from L-cysteine and L-selenocysteine, respectively, to form L-alanine. These enzymes are proposed to function as sulfur-delivery proteins for iron-sulfur cluster, thiamin, 4-thiouridine, biotin, and molybdopterin. Recently, it was reported that selenium mobilized from free selenocysteine is incorporated specifically into a selenoprotein and tRNA in vivo, supporting the involvement of the NifS-like proteins in selenium metabolism. We here report evidence that a strain lacking IscS is incapable of synthesizing 5-methylaminomethyl-2-selenouridine and its precursor 5-methylaminomethyl-2-thiouridine (mnm(5)s(2)U) in tRNA, suggesting that the sulfur atom released from L-cysteine by the action of IscS is incorporated into mnm(5)s(2)U. In contrast, neither CSD nor CsdB was essential for production of mnm(5)s(2)U and 5-methylaminomethyl-2-selenouridine. The lack of IscS also caused a significant loss of the selenium-containing polypeptide of formate dehydrogenase H. Together, these results suggest a dual function of IscS in sulfur and selenium metabolism.