Identification and synthesis of a naturally occurring selenonucleoside in bacterial tRNAs: 5-[(methylamino)methyl]-2-selenouridine

Wittwer, Arthur J.; Tsai, Lin; Ching, Wei Mei; Stadtman, Thressa C.

doi:10.1021/bi00315a021

Cited by 83 publications

(55 citation statements)

References 24 publications

(37 reference statements)

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“…Aliquots of supernatants containing 6-8 g of protein were analyzed for 75 Se-containing tRNA by SDS͞PAGE (12%) and PhosphorImager detection of radioactivity. 35 S-labeled tRNA was isolated as described (11,16). Nuclease digestion of tRNA was performed as described by Gehrke et al (33) with minor modifications.…”

Section: Methodsmentioning

confidence: 99%

“…Selenium is present as an essential selenocysteine residue in the polypeptide chains of various selenoproteins including bacterial formate dehydrogenase (9) and mammalian glutathione peroxidase (10). Seleniumcontaining tRNAs found in prokaryotes contain 5-methylaminomethyl-2-selenouridine (mnm 5 se 2 U) in the wobble position of the anticodons in glutamate, lysine, and glutamine isoaccepting tRNAs (11). The biosynthetic pathway for mnm 5 se 2 U has been partly characterized as shown in Fig.…”

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confidence: 99%

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TheiscSgene is essential for the biosynthesis of 2-selenouridine in tRNA and the selenocysteine-containing formate dehydrogenase H

Mihara

Kato

Lacourciere

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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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.

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

TheiscSgene is essential for the biosynthesis of 2-selenouridine in tRNA and the selenocysteine-containing formate dehydrogenase H

Mihara

Kato

Lacourciere

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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“…Selenium has been identified as a covalent base modification in tRNA from bacteria as well as mammals (Chen and Stadtman 1980;Ching and Stadtman 1982;Ching 1984;Wittwer et al 1984;Wittwer and Ching 1989;Kramer and Ames 1988;Ching 1984) and is incorporated into protein cotranslationally as the amino acid selenocysteine (Cone et al 1976;Forstrom et al 1978;Stadtman 1990;Bock et al 1991). Selenoproteins typically contain one selenocysteine moiety per peptide chain although the mammalian plasma protein, selenoprotein P, has been reported to have as many as 10 selenocysteine residues (Hill et al 1991(Hill et al , 1993.…”

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confidence: 99%

Recognition of the mRNA selenocysteine insertion sequence by the specialized translational elongation factor SELB.

Ringquist¹,

Schneider²,

Gibson³

et al. 1994

Genes Dev.

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In Escherichia coli the unusual amino acid selenocysteine is incorporated cotranslationally at an in-frame UGA codon. Incorporation of selenocysteine relies, in part, on the interaction between a specialized elongation factor, the SELB protein, and a cis-acting element within the mRNA. Boundary and toeprint experiments illustrate that the SELB-GTP-Sec-tRNA^''' ternary complex binds to the selenoprotein encoding mRNAs fdhF and fdnG, serving to increase the concentration of SELB and Sec-tRNA**'' on these mRNAs in vivo. Moreover, toeprint experiments indicate that SELB recognizes the ribosome-bound message and that, upon binding, SELB may protrude out of the ribosomal-mRNA track so as to approach the large ribosomal subunit. The results place the mRNA-bound SELB-GTP-Sec-tRNA^^'' ternary complex at the selenocysteine codon (as expected) and suggest a mechanism to explain the specificity of selenocysteine insertion. Cis-acting mRNA regulatory elements can tether protein factors to the translation complex during protein synthesis.

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“…Selenium is also incorporated into specific tRNA species in E. coli (40,42). Isoaccepting species of lysine and glutamate tRNA contain selenium (40).…”

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“…Isoaccepting species of lysine and glutamate tRNA contain selenium (40). The selenium is present in tRNA in the modified base 5-methylaminomethyl-2-selenouracil (mnm5Se2U) (40,42). This incorporation is believed to be specific for selenium due to the inability of vast excesses of sulfur in the culture medium to have a major effect on the selenium content of the tRNA (40).…”

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Isolation and characterization of a selenium metabolism mutant of Salmonella typhimurium

Kramer

Ames

1988

J Bacteriol

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Selenium is a constituent in Escherichia coli of the anaerobic enzyme formate dehydrogenase in the form of selenocysteine. Selenium is also present in the tRNA of E. coli in the modified base 5-methylaminomethyl-2-selenouracil (mnm5Se2U). The pathways of bacterial selenium metabolism are largely uncharacterized, and it is unclear whether nonspecific reactions in the sulfur metabolic pathways may be involved. We demonstrated that sulfur metabolic pathway mutants retak a wild-type pattern of selenium incorporation, indicating that selenite (SeO32) is metabolized entirely via selenium-specific pathways. To investigate the function of mnm5Se2U, we isolated a mutant which is unable to incorporate selenium into tRNA. This strain was obtained by isolating mutants lacking formate dehydrogenase activity and then screening for the inability to metabolize selenium. This phenotype is the result of a recessive mutation which appears to map in the general region of 21 min on the Salmonella typhimurium chromosome. A mutation in this gene, selA, thus has a pleiotropic effect of eliminating selenium incorporation into both protein and tRNA. The selA mutant appears to be blocked in a step of selenium metabolism after reduction, such as in the actual selenium insertion process. We showed that the absence of selenium incorporation into suppressor tRNA reduces the efficiency of suppression of nonsense codons in certain contexts and when wobble base pairing is required. Thus, one function of mnm5Se2U in tRNA may be in codon-anticodon interactions.

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Identification and synthesis of a naturally occurring selenonucleoside in bacterial tRNAs: 5-[(methylamino)methyl]-2-selenouridine

Cited by 83 publications

References 24 publications

TheiscSgene is essential for the biosynthesis of 2-selenouridine in tRNA and the selenocysteine-containing formate dehydrogenase H

TheiscSgene is essential for the biosynthesis of 2-selenouridine in tRNA and the selenocysteine-containing formate dehydrogenase H

Recognition of the mRNA selenocysteine insertion sequence by the specialized translational elongation factor SELB.

Isolation and characterization of a selenium metabolism mutant of Salmonella typhimurium

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