The iscS gene is essential for the biosynthesis of 2-selenouridine in tRNA and the selenocysteine-containing formate dehydrogenase H.
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.
Mihara
Hisaaki
H
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
Kato
Shin-ichiro
S
Lacourciere
Gerard M
GM
Stadtman
Thressa C
TC
Kennedy
Robert A J D
RA
Kurihara
Tatsuo
T
Tokumoto
Umechiyo
U
Takahashi
Yasuhiro
Y
Esaki
Nobuyoshi
N
D013437:Carbon-Sulfur Lyases / Q000235:genetics / Q000502:physiology*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005560:Formate Dehydrogenases / Q000096:biosynthesis*; D006864:Hydrogenase / Q000096:biosynthesis*; D009097:Multienzyme Complexes / Q000096:biosynthesis*; D016296:Mutagenesis; D016566:Organoselenium Compounds; D012343:RNA, Transfer / Q000096:biosynthesis*; D017279:Selenocysteine / Q000378:metabolism*; D013891:Thiouridine / Q000031:analogs & derivatives* / Q000378:metabolism*; D014529:Uridine / Q000031:analogs & derivatives / Q000096:biosynthesis*
D009097:Multienzyme Complexes; D016566:Organoselenium Compounds; D017279:Selenocysteine; D013891:Thiouridine; C011916:5-methylaminomethyl-2-thiouridine; C043608:5-((methylamino)methyl)-2-selenouridine; D012343:RNA, Transfer; D006864:Hydrogenase; D005560:Formate Dehydrogenases; C054017:formate hydrogenlyase; D013437:Carbon-Sulfur Lyases; C080546:cysteine desulfurase; D014529:Uridine