hIscA: a protein implicated in the biogenesis of iron–sulfur clusters

Cózar‐Castellano, Irene; Machargo, Marı́a del Valle; Trujillo, E.; Arteaga, Marı́a Francisca; González, Tomás; Martín‐Vasallo, Pablo; Ávila, Julio

doi:10.1016/j.bbapap.2004.05.004

Cited by 34 publications

(38 citation statements)

References 20 publications

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“…In S. cerevisiae, the homologue of IscA1, Isa1, is a mitochondrial protein and has a mitochondrial targeting sequence (7,22). Indeed, human IscA1 also is predicted to have a mitochondrial targeting sequence (21), and consistent with this, we find that most IscA1 is present in the mitochondrial fraction (Fig. 3B).…”

Section: Discussionsupporting

confidence: 72%

“…A clone that was isolated encoded for residues 48 -129 of human IscA1 (Unigene Hs.449291) (21). IscA1 is a homologue of the E. coli protein IscA (3), and at the mRNA level it is expressed in multiple tissues, including heart, kidney, cerebellum, and liver (21).…”

Section: Resultsmentioning

confidence: 99%

“…We generated HEK293 cells stably transfected with a doxycycline-inducible transgene expressing IscA1 R -(23-129) or with vector alone. IscA1 R -(23-129) lacks a mitochondrial targeting sequence predicted to be present in IscA1 (21), and its coding sequence contains three nucleotide substitutions in the region targeted by the IscA1 siRNA. We induced cells with doxycycline and treated them with siRNA.…”

Section: Volume 284 • Number 51 • December 18 2009mentioning

confidence: 99%

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Human ISCA1 Interacts with IOP1/NARFL and Functions in Both Cytosolic and Mitochondrial Iron-Sulfur Protein Biogenesis

Song

Lee

2009

Journal of Biological Chemistry

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Iron-sulfur proteins play an essential role in many biologic processes. Hence, understanding their assembly is an important goal. In Escherichia coli, the protein IscA is a product of the isc (iron-sulfur cluster) operon and functions in the iron-sulfur cluster assembly pathway in this organism. IscA is conserved in evolution, but its function in mammalian cells is not known. Here, we provide evidence for a role for a human homologue of IscA, named IscA1, in iron-sulfur protein biogenesis. We observe that small interfering RNA knockdown of IscA1 in HeLa cells leads to decreased activity of two mitochondrial iron-sulfur enzymes, succinate dehydrogenase and mitochondrial aconitase, as well as a cytosolic iron-sulfur enzyme, cytosolic aconitase. IscA1 is observed both in cytosolic and mitochondrial fractions. We find that IscA1 interacts with IOP1 (iron-only hydrogenase-like protein 1)/NARFL (nuclear prelamin A recognition factor-like), a cytosolic protein that plays a role in the cytosolic iron-sulfur protein assembly pathway. We therefore propose that human IscA1 plays an important role in both mitochondrial and cytosolic iron-sulfur cluster biogenesis, and a notable component of the latter is the interaction between IscA1 and IOP1.Iron-sulfur proteins play essential roles in pathways that include the Krebs cycle, oxidative phosphorylation, gene regulation, and purine metabolism (1, 2). Their assembly presents particular challenges in that iron is readily oxidized and can generate free radicals. Hence, there are specific pathways that participate in the assembly of iron-sulfur clusters. In bacteria such as Escherichia coli, there is a pathway dedicated to the assembly of iron-sulfur clusters (3). The isc operon is the central genetic locus for this pathway, and it contains genes that encode for the proteins that include IscS, IscU, and IscA. The key elements of this pathway include a mechanism for obtaining sulfur through the enzymatic activity of a cysteine desulfurase, a mechanism for combining sulfur with iron on scaffold proteins, and a means for delivery of the resultant iron-sulfur clusters to target apoproteins. It appears that these key elements have been conserved through evolution. Thus, the E. coli cysteine desulfurase IscS has homologues in Saccharomyces cerevisiae and mammalian cells, indicative of a central conserved function. Moreover, homologues of IscU and IscA also exist in yeast and mammalian cells. The exact function of these is less certain. For example, IscU has been proposed to be a scaffold of iron-sulfur cluster assembly in E. coli, S. cerevisiae, and mammals (4 -6). IscA has been proposed to serve as a scaffold for delivering iron-sulfur clusters to select target proteins in E. coli and S. cerevisiae or, alternatively, as an iron donor in E. coli (7-10); its role in mammalian cells is not known.In eukaryotic cells, the situation is made more complex by the necessity of having to assemble both mitochondrial and cytosolic iron-sulfur clusters. In S. cerevisiae, there are proteins dedicated...

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Section: Discussionsupporting

confidence: 72%

Section: Resultsmentioning

confidence: 99%

Section: Volume 284 • Number 51 • December 18 2009mentioning

confidence: 99%

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Human ISCA1 Interacts with IOP1/NARFL and Functions in Both Cytosolic and Mitochondrial Iron-Sulfur Protein Biogenesis

Song

Lee

2009

Journal of Biological Chemistry

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“…However, the iron donor(s) for the iron-sulfur cluster assembly still largely remains elusive. In this study we have compared the iron binding property of two putative iron donors for the iron-sulfur cluster assembly; CyaY, the bacterial ortholog of human frataxin (1,2), and IscA, a key member of the iron-sulfur cluster assembly machinery found in bacteria (35)(36)(37), yeast (38), and humans (39). The results demonstrate that IscA and CyaY have distinct iron binding properties under normal physiological and oxidative stress conditions.…”

Section: Discussionmentioning

confidence: 99%

“…In searching for specific iron donor(s) for biogenesis of ironsulfur clusters, we have discovered that IscA, a key member of the iron-sulfur cluster assembly machinery found in bacteria (35)(36)(37), yeast (38), and humans (39), is a novel iron-binding protein (40). In the presence of the thioredoxin reductase system, IscA binds iron with an iron association constant of 2.0 ϫ 10…”

mentioning

confidence: 99%

Distinct Iron Binding Property of Two Putative Iron Donors for the Iron-Sulfur Cluster Assembly

Ding

Yang

Coleman

et al. 2007

Journal of Biological Chemistry

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Frataxin, a small mitochondrial protein linked to the neurodegenerative disease Friedreich ataxia, has recently been proposed as an iron donor for the iron-sulfur cluster assembly. An analogous function has also been attributed to IscA, a key member of the iron-sulfur cluster assembly machinery found in bacteria, yeast, and humans. Here we have compared the iron binding property of IscA and the frataxin ortholog CyaY from Escherichia coli under physiological and oxidative stress conditions. In the presence of the thioredoxin reductase system, which emulates the intracellular redox potential, CyaY fails to bind any iron even at a 10-fold excess of iron in the incubation solution. Under the same physiologically relevant conditions, IscA efficiently recruits iron and transfers the iron for the ironsulfur cluster assembly in a proposed scaffold IscU. In the presence of hydrogen peroxide, however, IscA completely loses its iron binding activity, whereas CyaY becomes a competent ironbinding protein and attenuates the iron-mediated production of hydroxyl free radicals. Hydrogen peroxide appears to oxidize the iron binding thiol groups in IscA, thus blocking the iron binding in the protein. Once the oxidized thiol groups in IscA are re-reduced with the thioredoxin reductase system, the iron binding activity of IscA is fully restored. On the other hand, hydrogen peroxide has no effect on the iron binding carboxyl groups in CyaY, allowing the protein to bind iron under oxidative stress conditions. The results suggest that IscA is capable of recruiting intracellular iron for the iron-sulfur cluster assembly under normal physiological conditions, whereas CyaY may serve as an iron chaperon to sequester redox active free iron and alleviate cellular oxidative damage under oxidative stress conditions.Frataxin is a small mitochondrial protein that has been linked to Friedreich ataxia, an autosomal recessive neurodegenerative disease (1). Most Friedreich ataxia patients are homozygous for a large GAA repeat expansion in the first intron of the frataxin gene which impairs transcription and causes severe reduction in the level of frataxin in mitochondria (1, 2). Frataxin is highly conserved from bacteria to humans (3). Deletion of frataxin results in disruption of iron homeostasis and mitochondrial function in Saccharomyces cerevisiae (4), embryonic lethality in the mouse (5), and developmental arrest in the nematode Caenorhabditis elegans (6). Structural studies of human frataxin (7), yeast frataxin (8), and the bacterial frataxin ortholog CyaY 2 (9, 10) revealed a well conserved three-dimensional structure. However, the specific function of frataxin/CyaY is still not fully understood. Recently, it has been proposed that one of the functions of frataxin/CyaY may be involved in biogenesis of ironsulfur clusters, a group of ubiquitous redox co-factors in cells. This notion is primarily based on the observations that (i) depletion of frataxin in Friedreich ataxia patients is associated with deficiency of iron-sulfur proteins in mitoc...

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Prokaryotic Selenoproteins and Selenoproteomes

Zhang

2016

Selenium

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hIscA: a protein implicated in the biogenesis of iron–sulfur clusters

Cited by 34 publications

References 20 publications

Human ISCA1 Interacts with IOP1/NARFL and Functions in Both Cytosolic and Mitochondrial Iron-Sulfur Protein Biogenesis

Human ISCA1 Interacts with IOP1/NARFL and Functions in Both Cytosolic and Mitochondrial Iron-Sulfur Protein Biogenesis

Distinct Iron Binding Property of Two Putative Iron Donors for the Iron-Sulfur Cluster Assembly

Prokaryotic Selenoproteins and Selenoproteomes

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