Crystal structure of <i>Escherichia coli</i> YfhJ protein, a member of the ISC machinery involved in assembly of iron–sulfur clusters

Shimomura, Yoshimitsu; Takahashi, Yasuhiro; Kakuta, Yoshimitsu; Fukuyama, Keiichi

doi:10.1002/prot.20481

Cited by 28 publications

(26 citation statements)

References 35 publications

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“…An important component of SUF is the cysteine desulphurase, which contains the essential Isd11 protein in eukaryotes (Richards & van der Giezen, 2006). Isd11 is absent from eubacteria; instead bacterial cysteine desulphurase requires a distinct protein, YfhJ to function (Pastore et al ., 2006; Shimomura et al ., 2005). It seems YfhJ was lost early in eukaryotic evolution and was rapidly replaced by the eukaryotic Isd11.…”

Section: Mitochondrial Origins and Lecamentioning

confidence: 99%

Molecular paleontology and complexity in the last eukaryotic common ancestor

Koumandou

Wickstead

Ginger

et al. 2013

Critical Reviews in Biochemistry and Molecular Biology

183

192

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Eukaryogenesis, the origin of the eukaryotic cell, represents one of the fundamental evolutionary transitions in the history of life on earth. This event, which is estimated to have occurred over one billion years ago, remains rather poorly understood. While some well-validated examples of fossil microbial eukaryotes for this time frame have been described, these can provide only basic morphology and the molecular machinery present in these organisms has remained unknown. Complete and partial genomic information has begun to fill this gap, and is being used to trace proteins and cellular traits to their roots and to provide unprecedented levels of resolution of structures, metabolic pathways and capabilities of organisms at these earliest points within the eukaryotic lineage. This is essentially allowing a molecular paleontology. What has emerged from these studies is spectacular cellular complexity prior to expansion of the eukaryotic lineages. Multiple reconstructed cellular systems indicate a very sophisticated biology, which by implication arose following the initial eukaryogenesis event but prior to eukaryotic radiation and provides a challenge in terms of explaining how these early eukaryotes arose and in understanding how they lived. Here, we provide brief overviews of several cellular systems and the major emerging conclusions, together with predictions for subsequent directions in evolution leading to extant taxa. We also consider what these reconstructions suggest about the life styles and capabilities of these earliest eukaryotes and the period of evolution between the radiation of eukaryotes and the eukaryogenesis event itself.

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Section: Mitochondrial Origins and Lecamentioning

confidence: 99%

Molecular paleontology and complexity in the last eukaryotic common ancestor

Koumandou

Wickstead

Ginger

et al. 2013

Critical Reviews in Biochemistry and Molecular Biology

183

192

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“…This possibility is supported by an intrinsic ATPase activity of HscA, which is stimulated by HscB and by the interaction of the HscBA complex with the IscU scaffold (9,19,21,54,58). Neither the function of Fdx, which contains a redox-active [2Fe-2S] cluster, nor the function of IscX is known (26,27,53). IscR is a regulatory protein that apparently controls the expression of the isc gene cluster in a negative feedback loop that involves the assembly of a [2Fe-2S] cluster within IscR (52).…”

Section: Iron-sulfur Clusters ([Fementioning

confidence: 99%

Controlled Expression and Functional Analysis of Iron-Sulfur Cluster Biosynthetic Components within Azotobacter vinelandii

2006

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A system for the controlled expression of genes in Azotobacter vinelandii by using genomic fusions to the sucrose catabolic regulon was developed. This system was used for the functional analysis of the A. vinelandii isc genes, whose products are involved in the maturation of [Fe-S] proteins. For this analysis, the scrX gene, contained within the sucrose catabolic regulon, was replaced by the contiguous A. vinelandii iscS, iscU, iscA, hscB, hscA, fdx, and iscX genes, resulting in duplicate genomic copies of these genes: one whose expression is directed by the normal isc regulatory elements (Pisc) and the other whose expression is directed by the scrX promoter (

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“…Structural studies have shown that IscX (also called YfhJ) adopts a compact α-helical structure that exposes several acidic residues that mediate iron binding. 16,17 Previous studies also reported that IscX binds directly to IscS and suggested that it may play a role in Fe–S cluster assembly. 17,18 Intriguingly, bioinformatic analysis of genomes from various organisms found that the IscX gene co-occurs with that for IscS, whereas it correlates poorly with the presence of the gene for CyaY.…”

Section: Introductionmentioning

confidence: 98%

Role of IscX in Iron–Sulfur Cluster Biogenesis in Escherichia coli

et al. 2014

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The Escherichia coliisc operon encodes key proteins involved in the biosynthesis of iron–sulfur (Fe–S) clusters. Whereas extensive studies of most ISC proteins have revealed their functional properties, the role of IscX (also dubbed YfhJ), a small acidic protein encoded by the last gene in the operon, has remained in question. Previous studies showed that IscX binds iron ions and interacts with the cysteine desulfurase (IscS) and the scaffold protein for cluster assembly (IscU), and it has been proposed that IscX functions either as an iron supplier or a regulator of Fe–S cluster biogenesis. We have used a combination of NMR spectroscopy, small-angle X-ray scattering (SAXS), chemical cross-linking, and enzymatic assays to enlarge our understanding of the interactions of IscX with iron ions, IscU, and IscS. We used chemical shift perturbation to identify the binding interfaces of IscX and IscU in their complex. NMR studies showed that Fe2+ from added ferrous ammonium sulfate binds IscX much more avidly than does Fe3+ from added ferric ammonium citrate and that Fe2+ strengthens the interaction between IscX and IscU. We found that the addition of IscX to the IscU–IscS binary complex led to the formation of a ternary complex with reduced cysteine desulfurase activity, and we determined a low-resolution model for that complex from a combination of NMR and SAXS data. We postulate that the inhibition of cysteine desulfurase activity by IscX serves to reduce unproductive conversion of cysteine to alanine. By incorporating these new findings with results from prior studies, we propose a detailed mechanism for Fe–S cluster assembly in which IscX serves both as a donor of Fe2+ and as a regulator of cysteine desulfurase activity.

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Crystal structure of Escherichia coli YfhJ protein, a member of the ISC machinery involved in assembly of iron–sulfur clusters

Cited by 28 publications

References 35 publications

Molecular paleontology and complexity in the last eukaryotic common ancestor

Molecular paleontology and complexity in the last eukaryotic common ancestor

Controlled Expression and Functional Analysis of Iron-Sulfur Cluster Biosynthetic Components within Azotobacter vinelandii

Role of IscX in Iron–Sulfur Cluster Biogenesis in Escherichia coli

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