A paradigm for biological sulfur transfers via persulfide groups: a persulfide–disulfide–thiol cycle in 4-thiouridine biosynthesis

Wright, Chapman; Palenchar, Peter M.; Mueller, Eugene G.

doi:10.1039/b208626c

Cited by 30 publications

(32 citation statements)

References 21 publications

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“…This contrasts with our measurement of an apparent K m for cysteine in the coupled assay of 2.5 Ϯ 1.2 M. 2 Thus, sulfide binding by ThiI is weak (K m Ͼ20 mM) and physiologically irrelevant. However, the fact that sulfide is an efficient substrate at its optimal concentration provides some support for a mechanism of s 4 U synthesis in which nascent sulfide is produced by internal reduction of a ThiI persulfide (27). The alternative mechanism involves direct attack of a ThiI persulfide on the activated uridine before internal reduction.…”

Section: Discussionmentioning

confidence: 99%

“…We have shown through gel mobility shift assays that ThiI and not IscS binds to tRNA and that ThiI binds ATP, most probably for activation of the uridine via adenylation (22). The mechanism involves mobilization of sulfur from cysteine by IscS in the form of an enzyme-bound persulfide (23,24), which is then transferred to a cysteine residue on ThiI before final insertion into U8 of tRNA (25)(26)(27). The nature of the final sulfur transfer step is unclear, but it has been recently shown that ThiI is oxidized to a disulfide under single turnover conditions (28).…”

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confidence: 99%

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Substrate Specificity for 4-Thiouridine Modification in Escherichia coli

Lauhon

Erwin

Ton

2004

Journal of Biological Chemistry

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The biosynthesis of 4-thiouridine (s 4 U) in Escherichia coli tRNA requires the action of both the thiamin pathway enzyme ThiI and the cysteine desulfurase IscS. IscS catalyzes sulfur transfer from L-cysteine to ThiI, which utilizes Mg-ATP to activate uridine 8 in tRNA and transfers sulfur to give s 4 U. In this work, we show through deletion analysis of unmodified E. coli tRNA Phe that the minimum substrate for s 4 U modification is a mini-helix comprising the stacked acceptor and T stems containing an internal bulged region. The size of the bulged loop must be at least 4 nucleotides and contain the target uridine as the first nucleotide. Replacement of the T loop sequence with a tetraloop in the deletion substrate increases activity and shows that the T⌿C primary sequence is not a recognition element. An unmodified tRNA Phe transcript in which the 3 -terminal ACCA sequence is removed to give a blunt terminus has <0.1% activity, although the addition of a single overhanging base essentially restores activity. In addition, reducing the distance of the 3 terminus relative to U8 by as little as 1 bp severely impairs activity. By dissecting a minimal RNA substrate in the T loop region, a two-piece system consisting of a substrate RNA and a "guide" RNA is efficiently modified. Our results indicate that outside of the modified U8, there is no primary sequence requirement for substrate recognition. However, the secondary and tertiary structure restrictions appear sufficient to explain why s 4 U modification is limited in the cell to tRNA.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Substrate Specificity for 4-Thiouridine Modification in Escherichia coli

Lauhon

Erwin

Ton

2004

Journal of Biological Chemistry

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“…1). Two of them are arranged in a CXXC motif, and the third one is aligned in the sequence at an equivalent position as Cys 344 in the E. coli ThiI, which forms a disulfide bond with Cys 456 after sulfur transfer to tRNA U8 (30,32,33).…”

Section: Phylogenetic Distribution and Conserved Cys Residues Ofmentioning

confidence: 99%

“…During the sulfur transfer, the catalytically essential Cys 456 located in the RLD receives sulfur from IscS to form the ThiI persulfide (29 -31). After donation of the terminal sulfur of the ThiI persulfide to tRNA U8, Cys 456 forms a disulfide bond with Cys 344 located in the PP-loop domain (30,32,33). Presumably, the Cys 456 -Cys 344 disulfide needs to be reduced to complete the enzymatic cycle.…”

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confidence: 99%

Biosynthesis of 4-Thiouridine in tRNA in the Methanogenic Archaeon Methanococcus maripaludis

Liu

Zhu

Nakamura

et al. 2012

Journal of Biological Chemistry

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Background: Bacterial ThiI catalyzes 4-thiouridine biosynthesis by using a rhodanese-like domain for sulfur transfer. Results: ThiI in methanogenic archaea employs a conserved CXXC motif to generate persulfide and disulfide intermediates for sulfur transfer. Conclusion: Methanogens possess a unique sulfur relay strategy. Significance: Sulfur metabolism in methanogens is a model for the evolution of sulfur metabolism in the anaerobic sulfide-rich environments common on ancient earth.

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“…Experiments in vitro demonstrated the transfer of sulfur from the source cysteine via an IscS persulfide to form a ThiI persulfide (11) located at residue Cys456 (19). In 4-thiouridine biosynthesis, ThiI activates the tRNA uridine as its adenylate (30,32), which reacts with the Cys456 persulfide (11,19). Residue Cys344 then acts as a nucleophile, forming a Cys456-Cys344 disulfide and releasing 4-thiouridine.…”

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confidence: 99%

The Rhodanese Domain of ThiI Is Both Necessary and Sufficient for Synthesis of the Thiazole Moiety of Thiamine in Salmonella enterica

et al. 2011

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In Salmonella enterica, ThiI is a bifunctional enzyme required for the synthesis of both the 4-thiouridine modification in tRNA and the thiazole moiety of thiamine. In 4-thiouridine biosynthesis, ThiI adenylates the tRNA uridine and transfers sulfur from a persulfide formed on the protein. The role of ThiI in thiazole synthesis is not yet well understood. Mutational analysis described here found that ThiI residues required for 4-thiouridine synthesis were not involved in thiazole biosynthesis. The data further showed that the C-terminal rhodanese domain of ThiI was sufficient for thiazole synthesis in vivo. Together, these data support the conclusion that sulfur mobilization in thiazole synthesis is mechanistically distinct from that in 4-thiouridine synthesis and suggest that functional annotation of ThiI in genome sequences should be readdressed. Nutritional studies described here identified an additional cysteine-dependent mechanism for sulfur mobilization to thiazole that did not require ThiI, IscS, SufS, or glutathione. The latter mechanism may provide insights into the chemistry used for sulfur mobilization to thiazole in organisms that do not utilize ThiI.

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A paradigm for biological sulfur transfers via persulfide groups: a persulfide–disulfide–thiol cycle in 4-thiouridine biosynthesis

Cited by 30 publications

References 21 publications

Substrate Specificity for 4-Thiouridine Modification in Escherichia coli

Substrate Specificity for 4-Thiouridine Modification in Escherichia coli

Biosynthesis of 4-Thiouridine in tRNA in the Methanogenic Archaeon Methanococcus maripaludis

The Rhodanese Domain of ThiI Is Both Necessary and Sufficient for Synthesis of the Thiazole Moiety of Thiamine in Salmonella enterica

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