PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-3 (3)
 

Clipboard (0)
None
Journals
Authors
Year of Publication
Document Types
1.  Iron Binding Activity of Human Iron-Sulfur Cluster Assembly Protein hIscA-1 
The Biochemical journal  2010;428(1):125-131.
SYNOPSIS
A human homologue of the iron-sulfur cluster assembly protein IscA (hIscA1) has been cloned and expressed in Escherichia coli cells. The UV-visible absorption and EPR (electron paramagnetic resonance) measurements reveal that hIscA1 purified from E. coli cells contains a mononuclear iron center and that the iron binding in hIscA1 expressed in E. coli cells can be further modulated by the iron content in the cell growth medium. Additional studies show that purified hIscA1 binds iron with an iron association constant of approx. 2.0 × 1019 M−1, and that the iron-bound hIscA1 is able to provide the iron for the iron-sulfur cluster assembly in a proposed scaffold protein IscU of E. coli in vitro. The complementation experiments indicate that hIscA1 can partially substitute for IscA in restoring the cell growth of E. coli in the M9 minimal medium under aerobic conditions. The results suggest that human IscA1, like E. coli IscA, is an iron binding protein that may act as an iron chaperone for biogenesis of iron-sulfur clusters.
doi:10.1042/BJ20100122
PMCID: PMC2878720  PMID: 20302570
Iron-sulfur cluster biogenesis; human IscA homologue; intracellular iron content
2.  IscA/SufA Paralogs Are Required for the [4Fe-4S] Cluster Assembly in Enzymes of Multiple Physiological Pathways in Escherichia coli under Aerobic Growth Conditions 
The Biochemical journal  2009;420(3):463-472.
Synopsis
IscA/SufA paralogs are the members of the iron-sulfur cluster assembly machinery in Escherichia coli. While deletion of either IscA or SufA has only a mild effect on cell growth, deletion of both IscA and SufA results in a null-growth phenotype in minimal medium under aerobic growth conditions. Here we report that cell growth of the iscA/sufA double mutant (E. coli strain in which both iscA and sufA had been in-frame-deleted) can be partially restored by supplementing with BCAAs (branched-chain amino acids) and thiamin. We further demonstrate that deletion of IscA/SufA paralogs blocks the [4Fe-4S] cluster assembly in IlvD (dihydroxyacid dehydratase) of the BCAA biosynthesis pathway in E. coli cells under aerobic conditions and that addition of the iron-bound IscA/SufA efficiently promotes the [4Fe-4S] cluster assembly in IlvD and restores the enzyme activity in vitro, suggesting that IscA/SufA may act as an iron donor for the [4Fe-4S] cluster assembly under aerobic conditions. Additional studies reveal that IscA/SufA are also required for the [4Fe-4S] cluster assembly in protein ThiC of the thiamin biosynthesis pathway, aconitase B of the citrate acid cycle, and endonuclease III of the DNA base excision repair pathway in E. coli under aerobic conditions. Nevertheless, deletion of IscA/SufA does not significantly affect the [2Fe-2S] cluster assembly in the redox transcription factor SoxR, ferredoxin, and the siderophore-iron reductase FhuF. The results suggest that the biogenesis of the [4Fe-4S] clusters and the [2Fe-2S] clusters may have distinct pathways and that IscA/SufA paralogs are essential for the [4Fe-4S] cluster assembly, but are dispensable for the [2Fe-2S] cluster assembly in E. coli under aerobic conditions.
doi:10.1042/BJ20090206
PMCID: PMC2776711  PMID: 19309314
aconitase; branched-chain amino acids; dihydroxyacid dehydratase; iron-sulfur clusters; IscA/SufA paralogs; thiamin
3.  Escherichia coli FtnA Acts as an Iron Buffer for Re-assembly of Iron-Sulfur Clusters in Response to Hydrogen Peroxide Stress 
Iron-sulfur clusters are one of the most ubiquitous redox centers in biology. Ironically, iron-sulfur clusters are highly sensitive to reactive oxygen species. Disruption of iron-sulfur clusters will not only change the activity of proteins that host iron-sulfur clusters, the iron released from the disrupted iron-sulfur clusters will further promote the production of deleterious hydroxyl free radicals via the Fenton reaction. Here, we report that ferritin A (FtnA), a major iron-storage protein in Escherichia coli, is able to scavenge the iron released from the disrupted iron-sulfur clusters and alleviates the production of hydroxyl free radicals. Furthermore, we find that the iron stored in ferritin A can be retrieved by an iron chaperon IscA for the re-assembly of the iron-sulfur cluster in a proposed scaffold IscU in the presence of the thioredoxin reductase system which emulates normal intracellular redox potential. The results suggest that E. coli ferritin A may act as an iron buffer to sequester the iron released from the disrupted iron-sulfur clusters under oxidative stress conditions and to facilitate the re-assembly of the disrupted iron-sulfur clusters under normal physiological conditions.
doi:10.1007/s10534-008-9154-7
PMCID: PMC2576483  PMID: 18618270
Ferritin A; hydroxyl free radicals; iron-sulfur clusters; IscA; IscU

Results 1-3 (3)