Crystal Structure of IscS, a Cysteine Desulfurase from Escherichia coli

Cupp‐Vickery, Jill R.; Urbina, Hugo D.; Vickery, Larry E.

doi:10.1016/s0022-2836(03)00690-9

Cited by 162 publications

(191 citation statements)

References 41 publications

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“…In both the T. maritima (37) and E. coli (38) structures, portions of this loop are disordered, consistent with its proposed flexibility. Neither Leu 333 of E. coli IscS nor the equivalent of Glu 329 in T. maritima NifS was observable in the crystal structure.…”

Section: Discussionsupporting

confidence: 64%

“…Structural data from a crystal form of E. coli IscS shows that the loop containing the C328 can be positioned near the protein surface, greater than 17 Å from the buried pyridoxal phosphate cofactor (38). In both the T. maritima (37) and E. coli (38) structures, portions of this loop are disordered, consistent with its proposed flexibility.…”

Section: Discussionmentioning

confidence: 81%

“…In the crystal structures of IscS from Thermotoga maritima (37) and E. coli IscS (38), portions of the loop are unstructured. Models of the unresolved region of the loop in E. coli IscS both place Cys 328 at least 17 Å from the active site pyridoxal phosphate (38) and support the suggestion that a flexible loop would allow transfer of the persulfide sulfur at a greater distance to protein substrates (37). Because the role of iscS in E. coli requires distribution of sulfur for a variety of pathways, a major question is how specificity is manifested in sulfur transfer from IscS to each of its protein substrates.…”

mentioning

confidence: 99%

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Substitutions in an Active Site Loop of Escherichia coli IscS Result in Specific Defects in Fe-S Cluster and Thionucleoside Biosynthesis in Vivo

Lauhon

Skovran

Urbina

et al. 2004

Journal of Biological Chemistry

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IscS catalyzes the fragmentation of L-cysteine to Lalanine and sulfane sulfur in the form of a cysteine persulfide in the active site of the enzyme. In Escherichia coli IscS, the active site cysteine Cys 328 resides in a flexible loop that potentially influences both the formation and stability of the cysteine persulfide as well as the specificity of sulfur transfer to protein substrates. Alanine-scanning substitution of this 14 amino acid region surrounding Cys 328 identified additional residues important for IscS function in vivo. Two mutations, S326A and L333A, resulted in strains that were severely impaired in Fe-S cluster synthesis in vivo. The mutant strains were deficient in Fe-S cluster-dependent tRNA thionucleosides (s 2 C and ms 2 i 6 A) yet showed wild type levels of Fe-S-independent thionucleosides (s 4 U and mnm 5 s 2 U) that require persulfide formation and transfer. In vitro, the mutant proteins were similar to wild type in both cysteine desulfurase activity and sulfur transfer to IscU. These results indicate that residues in the active site loop can selectively affect Fe-S cluster biosynthesis in vivo without detectably affecting persulfide delivery and suggest that additional assays may be necessary to fully represent the functions of IscS in Fe-S cluster formation.

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Section: Discussionsupporting

confidence: 64%

Section: Discussionmentioning

confidence: 81%

mentioning

confidence: 99%

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Substitutions in an Active Site Loop of Escherichia coli IscS Result in Specific Defects in Fe-S Cluster and Thionucleoside Biosynthesis in Vivo

Lauhon

Skovran

Urbina

et al. 2004

Journal of Biological Chemistry

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“…This finding suggests that sulfur transfer from IscS is more facile and is less tightly controlled than from SufS. The recently solved crystal structure of IscS supports this hypothesis (39). In contrast to the buried active site in the SufS structure, the active site Cys residue of IscS is located on a flexible loop that is more exposed to the external environment.…”

Section: Discussionmentioning

confidence: 95%

The SufE Protein and the SufBCD Complex Enhance SufS Cysteine Desulfurase Activity as Part of a Sulfur Transfer Pathway for Fe-S Cluster Assembly in Escherichia coli

Outten

Wood

Muñoz

et al. 2003

Journal of Biological Chemistry

264

375

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The sufABCDSE operon of the Gram-negative bacterium Escherichia coli is induced by oxidative stress and iron deprivation. To examine the biochemical roles of the Suf proteins, we purified all of the proteins and assayed their effect on SufS cysteine desulfurase activity. Here we report that the SufE protein can stimulate the cysteine desulfurase activity of the SufS enzyme up to 8-fold and accepts sulfane sulfur from SufS. This sulfur transfer process from SufS to SufE is sheltered from the environment based on its resistance to added reductants and on the analysis of available crystal structures of the proteins. We also found that the SufB, SufC, and SufD proteins associate in a stable complex and that, in the presence of SufE, the SufBCD complex further stimulates SufS activity up to 32-fold. Thus, the SufE protein and the SufBCD complex act synergistically to modulate the cysteine desulfurase activity of SufS. We propose that this sulfur transfer mechanism may be important for limiting sulfide release during oxidative stress conditions in vivo.

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“…In E. coli, IscS activity is necessary for the mobilization of S for the maturation of various cofactors and proteins (Takahashi and Nakamura, 1999;Schwartz et al, 2000;Tokumoto and Takahashi, 2001;Lauhon and Kampampti, 2000). The crystal structure of IscS has been determined (Cupp-Vickery et al, 2003). IscU is a truncated version of NifU, containing the N-terminal domain of NifU (Yuvaniyama et al, 2000).…”

Section: Biosynthesis Of Fe-s Clustersmentioning

confidence: 99%

Molecular Biology of Microbial Hydrogenases

2004

Current Issues in Molecular Biology

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Crystal Structure of IscS, a Cysteine Desulfurase from Escherichia coli

Cited by 162 publications

References 41 publications

Substitutions in an Active Site Loop of Escherichia coli IscS Result in Specific Defects in Fe-S Cluster and Thionucleoside Biosynthesis in Vivo

Substitutions in an Active Site Loop of Escherichia coli IscS Result in Specific Defects in Fe-S Cluster and Thionucleoside Biosynthesis in Vivo

The SufE Protein and the SufBCD Complex Enhance SufS Cysteine Desulfurase Activity as Part of a Sulfur Transfer Pathway for Fe-S Cluster Assembly in Escherichia coli

Molecular Biology of Microbial Hydrogenases

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