IscR‐dependent gene expression links iron‐sulphur cluster assembly to the control of O<sub>2</sub>‐regulated genes in <i>Escherichia coli</i>

Giel, Jennifer L.; Rodionov, Dmitry A.; Liu, Mingzhu; Blattner, Frederick R.; Kiley, Patricia J.

doi:10.1111/j.1365-2958.2006.05160.x

Cited by 251 publications

(409 citation statements)

References 64 publications

Supporting

Mentioning

391

Contrasting

Unclassified

Order By: Relevance

“…The enzyme is synthesized under anaerobic conditions, and its expression is switched off in a fully oxic environment (36)(37)(38). A coexpressed cytochrome bd-II oxidase (39) is thought to complete this short respiratory electron transport chain between H 2 and O 2 under microaerobic conditions.…”

Section: Assay Of Intermolecular Electron-transfer Kinetics Using Cytmentioning

confidence: 99%

How oxygen reacts with oxygen-tolerant respiratory [NiFe]-hydrogenases

Wulff

Day

Sargent

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

An oxygen-tolerant respiratory [NiFe]-hydrogenase is proven to be a four-electron hydrogen/oxygen oxidoreductase, catalyzing the reaction 2 H 2 + O 2 = 2 H 2 O, equivalent to hydrogen combustion, over a sustained period without inactivating. At least 86% of the H 2 O produced by Escherichia coli hydrogenase-1 exposed to a mixture of 90% H 2 and 10% O 2 is accounted for by a direct four-electron pathway, whereas up to 14% arises from slower side reactions proceeding via superoxide and hydrogen peroxide. The direct pathway is assigned to O 2 reduction at the [NiFe] active site, whereas the side reactions are an unavoidable consequence of the presence of low-potential relay centers that release electrons derived from H 2 oxidation. The oxidase activity is too slow to be useful in removing O 2 from the bacterial periplasm; instead, the four-electron reduction of molecular oxygen to harmless water ensures that the active site survives to catalyze sustained hydrogen oxidation.hydrogen | mass spectrometry | Fe-S cluster H ydrogenases are enzymes that catalyze the interconversion of H 2 and H + with great efficiency. Containing Fe or Fe and Ni as active metals, they are not only important in biohydrogen production (by fermentative and photosynthetic means) but also provide inspiration for detailed understanding and development of optimal molecular electrocatalysts. The minimal active site motif, common to all hydrogenases, is a low-spin Fe atom coordinated by CO, CN − , and thiolate ligands, a combination expected to be unstable under aerobic conditions. Indeed, most hydrogenases suffer long-term or permanent inactivation when exposed to even traces of O 2 . It is therefore of special interest that certain [NiFe]-hydrogenases have evolved to sustain H 2 oxidation in the continued presence of O 2 , without inactivation: these enzymes are known as O 2 -tolerant [NiFe]-hydrogenases.Most of our current insight into the mechanism of O 2 tolerance stems from studies on respiratory membrane-bound [NiFe]-hydrogenases that couple H 2 oxidation to reduction of quinones (1-3). These enzymes are localized at the cytoplasmic membrane and project into the periplasmic space. A model proposed for the O 2 -tolerance mechanism of these [NiFe]-hydrogenases ( Fig. 1) is based on the following evidence. Oxygen reacts with O 2 -tolerant membrane-bound [NiFe]-hydrogenases to form, exclusively, an inactive state known as Ni-B or "ready," formulated as a Ni(III)-OH species, which is rapidly reactivated by one-electron transfer to rejoin the catalytic cycle of H 2 oxidation. Provided Ni-B is the sole product of O 2 attack, the presence of O 2 merely attenuates the steady-state rate of H 2 oxidation. In contrast, standard (O 2 sensitive) [NiFe]-hydrogenases react with O 2 to give a mixture of states, including ones variously known as "unready" or Ni-A, in which O 2 is either only partially reduced (possibly trapped as a peroxide) or has oxygenated atoms of the active site (3-7). The unready states are only reactivated very slowly; consequently, t...

show abstract

Section: Assay Of Intermolecular Electron-transfer Kinetics Using Cytmentioning

confidence: 99%

How oxygen reacts with oxygen-tolerant respiratory [NiFe]-hydrogenases

Wulff

Day

Sargent

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…Although direct binding of RirA to DNA has not been reported, a DNA sequence necessary for RirA-dependent regulation was identified (63,64,75). The ligand that imparts iron responsiveness to RirA has not been established, although the related Rrf2-type protein IscR binds and responds to Fe-S clusters, and it has been suggested that RirA also binds Fe-S clusters (19,31,58). Agrobacterium tumefaciens is also a well-studied member of the Alphaproteobacteria, related to both B. japonicum and R. leguminosarum (7,53).…”

mentioning

confidence: 99%

Antiparallel and Interlinked Control of Cellular Iron Levels by the Irr and RirA Regulators of Agrobacterium tumefaciens

Hibbing

Fuqua

2011

J Bacteriol

View full text Add to dashboard Cite

The plant pathogen Agrobacterium tumefaciens encodes predicted iron-responsive regulators, Irr and RirA, that function in several other bacteria to control the response to environmental iron levels. Deletion mutations of irr and rirA, alone and in combination, were evaluated for their impact on cellular iron response. Growth was severely diminished in the ⌬irr mutant under iron-limiting conditions, but reversed to wild-type levels in an ⌬irr ⌬rirA mutant. The level of uncomplexed iron in the ⌬irr mutant was decreased, whereas the ⌬rirA mutant exhibited elevated iron levels. Sensitivity of the ⌬irr and ⌬rirA mutants to iron-activated antimicrobial compounds generally reflected their uncomplexed-iron levels. Expression of genes that encode iron uptake systems was decreased in the ⌬irr mutant, whereas that of iron utilization genes was increased. Irr function required a trihistidine repeat likely to mediate interactions with heme. Iron uptake genes were derepressed in the ⌬rirA mutant. In the ⌬irr ⌬rirA mutant, iron uptake and utilization genes were derepressed, roughly combining the phenotypes of the single mutants. Siderophore production was elevated in the rirA mutant, but most strongly regulated by an RirA-controlled sigma factor. Expression of rirA itself was regulated by Irr, RirA, and iron availability, in contrast to irr expression, which was relatively stable in the different mutants. These studies suggest that in A. tumefaciens, the Irr protein is most active under low-iron conditions, inhibiting iron utilization and activating iron acquisition, while the RirA protein is active under high-iron conditions, repressing iron uptake.

show abstract

“…For example, IscR of E. coli binds to a slight upstream of 235 sequence and induces expression of some target genes, while it also binds to a site partly overlapped with 210 sequence and represses expression of other target genes (Giel et al, 2006). Our data revealed that the Slr0846-binding sequence is located more than 150 bp upstream from the transcription start point P1 in the psaA-6/5 region, although the precise binding motif has not yet been elucidated.…”

Section: The Mechanism Of Transcriptional Activation By Slr0846mentioning

confidence: 87%

An Rrf2-Type Transcriptional Regulator Is Required for Expression of psaAB Genes in the Cyanobacterium Synechocystis sp. PCC 6803

et al. 2009

View full text Add to dashboard Cite

Photosynthetic organisms must regulate photosystem stoichiometry (photosystem I-to-photosystem II ratio) under various light conditions. Transcriptional regulation of the psaAB genes is a critical process for this photoacclimation in cyanobacteria. In the course of our screening of transcriptional regulators in the cyanobacterium Synechocystis sp. PCC 6803, we found that chlorophyll accumulation was impaired in an Rrf2-type regulator Slr0846 mutant. DNA microarray and primer extension analyses showed that the expression of psaAB genes was markedly decreased in the mutant. Consistently, the mutant exhibited lower photosystem I-to-photosystem II ratio under normal light conditions, suggestive of decreased accumulation of the photosystem I reaction center. Gel-shift assay confirmed that the Slr0846 protein bound to a far upstream promoter region of psaAB. These phenotypes of the mutant varied substantially with light conditions. These results suggest that Slr0846 is a novel transcriptional regulator for optimal expression of psaAB.

show abstract

IscR‐dependent gene expression links iron‐sulphur cluster assembly to the control of O₂‐regulated genes in Escherichia coli

Cited by 251 publications

References 64 publications

How oxygen reacts with oxygen-tolerant respiratory [NiFe]-hydrogenases

How oxygen reacts with oxygen-tolerant respiratory [NiFe]-hydrogenases

Antiparallel and Interlinked Control of Cellular Iron Levels by the Irr and RirA Regulators of Agrobacterium tumefaciens

An Rrf2-Type Transcriptional Regulator Is Required for Expression of psaAB Genes in the Cyanobacterium Synechocystis sp. PCC 6803

Contact Info

Product

Resources

About

IscR‐dependent gene expression links iron‐sulphur cluster assembly to the control of O2‐regulated genes in Escherichia coli

Cited by 251 publications

References 64 publications

How oxygen reacts with oxygen-tolerant respiratory [NiFe]-hydrogenases

How oxygen reacts with oxygen-tolerant respiratory [NiFe]-hydrogenases

Antiparallel and Interlinked Control of Cellular Iron Levels by the Irr and RirA Regulators of Agrobacterium tumefaciens

An Rrf2-Type Transcriptional Regulator Is Required for Expression of psaAB Genes in the Cyanobacterium Synechocystis sp. PCC 6803

Contact Info

Product

Resources

About

IscR‐dependent gene expression links iron‐sulphur cluster assembly to the control of O₂‐regulated genes in Escherichia coli