scholarly journals Multiple Sense and Antisense Promoters Contribute to the Regulated Expression of the isc-suf Operon for Iron-Sulfur Cluster Assembly in Rhodobacter

2019 ◽  
Vol 7 (12) ◽  
pp. 671 ◽  
Author(s):  
Xin Nie ◽  
Bernhard Remes ◽  
Gabriele Klug
Keyword(s):  
Rhodobacter Sphaeroides ◽  
Photosynthetic Electron Transport ◽  
Regulatory Proteins ◽  
Cluster Assembly ◽  
Iron Sulfur Cluster ◽  
Iron Sulfur Clusters ◽  
Sulfur Cluster ◽  
Iron Sulfur ◽  
Photosynthetic Complexes ◽  
The One

A multitude of biological functions relies on iron-sulfur clusters. The formation of photosynthetic complexes goes along with an additional demand for iron-sulfur clusters for bacteriochlorophyll synthesis and photosynthetic electron transport. However, photooxidative stress leads to the destruction of iron-sulfur clusters, and the released iron promotes the formation of further reactive oxygen species. A balanced regulation of iron-sulfur cluster synthesis is required to guarantee the supply of this cofactor, on the one hand, but also to limit stress, on the other hand. The phototrophic alpha-proteobacterium Rhodobacter sphaeroides harbors a large operon for iron-sulfur cluster assembly comprising the iscRS and suf genes. IscR (iron-sulfur cluster regulator) is an iron-dependent regulator of isc-suf genes and other genes with a role in iron metabolism. We applied reporter gene fusions to identify promoters of the isc-suf operon and studied their activity alone or in combination under different conditions. Gel-retardation assays showed the binding of regulatory proteins to individual promoters. Our results demonstrated that several promoters in a sense and antisense direction influenced isc-suf expression and the binding of the IscR, Irr, and OxyR regulatory proteins to individual promoters. These findings demonstrated a complex regulatory network of several promoters and regulatory proteins that helped to adjust iron-sulfur cluster assembly to changing conditions in Rhodobacter sphaeroides.

Biogenesis and Transfer of Iron-Sulfur Clusters from Acidithiobacillus ferrooxidans

2013 ◽  
Vol 825 ◽  
pp. 198-201 ◽  
Author(s):  
Jian She Liu ◽  
Lin Qian ◽  
Chun Li Zheng
Keyword(s):  
Acidithiobacillus Ferrooxidans ◽  
Binding Protein ◽  
Cluster Assembly ◽  
Cysteine Desulfurase ◽  
Iron Sulfur Cluster ◽  
Iron Sulfur Clusters ◽  
Sulfur Cluster ◽  
Iron Sulfur ◽  
Iron Sulfur Proteins

Iron-sulfur (Fe-S) proteins are ubiquitous and participate in multiple essential functions of life. However, little is currently known about the mechanisms of iron-sulfur biosynthesis and transfer in acidophilic microorganisms. In this study, the IscS, IscU and IscA proteins from Acidithiobacillus ferrooxidans were successfully expressed in Escherichia coli and purified by affinity chromatography. The IscS was a cysteine desulfurase which catalyzes desulfurization of L-cysteine and transfer sulfur for iron-sulfur cluster assembly. Purified IscU did not have an iron-sulfur cluster but could act as a scaffold protein to assemble the [2Fe-2S] cluster in vitro. The IscA was a [4Fe-4S] cluster binding protein, but it also acted as an iron binding protein. Further studies indicated that the iron sulfur clusters could be transferred from pre-assembled scaffold proteins to apo-form iron sulfur proteins, the reconstituted iron sulfur proteins could restore their physiological activities.

scholarly journals Bridging a gap in iron-sulfur cluster assembly

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Erin L. McCarthy ◽  
Squire J. Booker
Keyword(s):  
Adaptor Proteins ◽  
Cluster Assembly ◽  
Iron Sulfur Cluster ◽  
Iron Sulfur Clusters ◽  
Sulfur Cluster ◽  
Iron Sulfur ◽  
Cellular Machinery

The cellular machinery that incorporates iron-sulfur clusters into proteins is directed to particular targets by adaptor proteins.

Complementary roles of SufA and IscA in the biogenesis of iron–sulfur clusters in Escherichia coli

2007 ◽  
Vol 409 (2) ◽  
pp. 535-543 ◽  
Author(s):  
Jianxin Lu ◽  
Juanjuan Yang ◽  
Guoqiang Tan ◽  
Huangen Ding
Keyword(s):  
Cell Growth ◽  
Double Mutant ◽  
Iron Binding ◽  
Cluster Assembly ◽  
Iron Sulfur Cluster ◽  
Iron Sulfur Clusters ◽  
Sulfur Cluster ◽  
E Coli ◽  
Iron Sulfur ◽  
Iron Binding Protein

Biogenesis of iron–sulfur clusters requires a concerted delivery of iron and sulfur to target proteins. It is now clear that sulfur in iron–sulfur clusters is derived from L-cysteine via cysteine desulfurases. However, the specific iron donor for the iron–sulfur cluster assembly still remains elusive. Previous studies showed that IscA, a member of the iron–sulfur cluster assembly machinery in Escherichia coli, is a novel iron-binding protein, and that the iron-bound IscA can provide iron for the iron–sulfur cluster assembly in a proposed scaffold IscU in vitro. However, genetic studies have indicated that IscA is not essential for the cell growth of E. coli. In the present paper, we report that SufA, an IscA paralogue in E. coli, may represent the redundant activity of IscA. Although deletion of IscA or SufA has only a mild effect on cell growth, deletion of both IscA and SufA in E. coli results in a severe growth phenotype in minimal medium under aerobic growth conditions. Cell growth is restored when either IscA or SufA is re-introduced into the iscA−/sufA− double mutant, demonstrating further that either IscA or SufA is sufficient for their functions in vivo. Purified SufA, like IscA, is an iron-binding protein that can provide iron for the iron–sulfur cluster assembly in IscU in the presence of a thioredoxin reductase system which emulates the intracellular redox potential. Site-directed mutagenesis studies show that the SufA/IscA variants that lose the specific iron-binding activity fail to restore the cell growth of the iscA−/sufA− double mutant. The results suggest that SufA and IscA may constitute the redundant cellular activities to recruit intracellular iron and deliver iron for the iron–sulfur cluster assembly in E. coli.

scholarly journals Regulation of the HscA ATPase Reaction Cycle by the Co-chaperone HscB and the Iron-Sulfur Cluster Assembly Protein IscU

2004 ◽  
Vol 279 (52) ◽  
pp. 53924-53931 ◽  
Author(s):  
Jonathan J. Silberg ◽  
Tim L. Tapley ◽  
Kevin G. Hoff ◽  
Larry E. Vickery
Keyword(s):  
Cluster Assembly ◽  
Iron Sulfur Cluster ◽  
Reaction Cycle ◽  
Sulfur Cluster ◽  
Iron Sulfur ◽  
Atpase Reaction

scholarly journals Interplay between formation of photosynthetic complexes and expression of genes for iron–sulfur cluster assembly in Rhodobacter sphaeroides?

2020 ◽  
Vol 147 (1) ◽  
pp. 39-48
Author(s):  
Xin Nie ◽  
Andreas Jäger ◽  
Janek Börner ◽  
Gabriele Klug
Keyword(s):  
Rhodobacter Sphaeroides ◽  
Cluster Formation ◽  
Rna Stability ◽  
Photosynthetic Apparatus ◽  
Growth Conditions ◽  
Cluster Assembly ◽  
Iron Sulfur Cluster ◽  
Expression Of Genes ◽  
Photosynthetic Complexes ◽  
Photosynthesis Genes

AbstractFormation of photosynthetic complexes leads to a higher demand for Fe–S clusters. We hypothesized that in the facultative phototrophic alpha-proteobacterium Rhodobacter sphaeroides expression of the isc-suf operon for Fe–S cluster formation may be increased under conditions that promote formation of photosynthetic complexes and that, vice versa, lack of the IscR regulator may also affect photosynthesis gene expression. To test this hypothesis, we monitored the activities of the isc-suf sense and anti-sense promoters under different growth conditions and in mutants which are impaired in formation of photosynthetic complexes. We also tested expression of photosynthesis genes in a mutant lacking the IscR regulator. Our results are not in agreement with a co-regulation of the Isc-Suf system and the photosynthetic apparatus at level of transcription. We provide evidence that, coordination of the systems occurs at post-transcriptional levels. Increased levels of isc-suf mRNAs under conditions promoting formation of photosynthetic complexes are due to higher RNA stability.

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