FNR‐dependent repression of the <i>ndh</i> gene of <i>Escherichia coli</i> and metal ion requirement for FNR‐regulated gene expression

Spiro, Stephen; Roberts, Ruth E.; Guest, John R.

doi:10.1111/j.1365-2958.1989.tb00207.x

Cited by 147 publications

(116 citation statements)

References 35 publications

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“…The results show that open complex is formed only under anaerobic conditions when FNR is present and they confirm previous observations that chelating agents inhibit the FNR-dependent expression of appro= priate 1ac.Z fusions [7]. The inhibitory effects of chelators on la& expression could be prevented by the prior addition of metal ions, ferrous iron being the most effective.…”

Section: The Effect Of Ferrozine On Open Complex Formation At the Ff-mentioning

confidence: 80%

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A role for iron in transcriptional activation by FNR

Green

Guest

1993

FEBS Letters

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FNR is a tmn~~ption~ regulator which controls the expression of target genes in response to anoxia in ~scberich~ c&i. The m~hanism by which FNR senses and responds to anaerobiosis is unknown but indirect evidence suggests that an iron cofactor is involved. Using KMnO, as a probe for DNA melting at active promoters, footprinting studies have now shown that the ferrous iron chelator, ferrozine, inhibits open complex formation in vivo, and that FNR with a high iron-content is essential for open complex formation in vitro. Since open complex formation is an essential pre-requisite for transcription, it is concluded that transcriptional activation by FNR is mediated by a ferrous iron cofactor.

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Section: The Effect Of Ferrozine On Open Complex Formation At the Ff-mentioning

confidence: 80%

“…Second, chelating agents mimic oxygen in preventing the anaerobic activation or repression of FNR regulated genes [7] and by increasing the rate of cysteine-residue carboxymethylation in the FNR of permeabilized cells [8]. Third, purified FNR protein contains two forms differing in the presence of a disCorrespondence address: J.R.…”

Section: Introductionmentioning

confidence: 99%

A role for iron in transcriptional activation by FNR

Green

Guest

1993

FEBS Letters

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“…Each set of 1acnA-lacZ monolysogens consisted of a parental strain, a regulator mutant, and the mutant containing a multicopy plasmid expressing the wild-type regulator gene, respectively for the following regulators : CRP [MClOOO, JRG1999, and JRGl999(pGS279) Table 1. Analogous Afkz-lacZ monolysogens were isolated with the Fur set of hosts using the fusion phages described previously by Woods 8c Guest (1987): 1G185 (AfumA-lacZ) ; 1G186 (LfumB-lad) ; and 1G187 (1fumC-lacz) ; see Fig. 1.…”

Section: Bacterial Strains Plasmids Phagemids and Bacteriophagesmentioning

confidence: 99%

“…1). The fusion was then transferred to 1RZ5 (M. Berman) by in vivo recombination in strain RK4353(pGS563) according to Spiro & Guest (1987). The corresponding 1acnA-lac2 fusion phage (1G244) was established as a single-copy prophage in different sets of host strains for investigating the roles of global regulators in acnA expression.…”

Section: Bacterial Strains Plasmids Phagemids and Bacteriophagesmentioning

confidence: 99%

Two genetically-distinct and differentially-regulated aconitases (AcnA and AcnB) in Escherichia coli

1994

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“…Several studies (3)(4)(5)(6)(7)(8) suggest that iron is also required for regulation of FNR activity by oxygen. For example, the transcription activating function of FNR can be manipulated in vitro (6,7) and in vivo (6,8) by Fe2+ levels.…”

mentioning

confidence: 99%

Association of a polynuclear iron-sulfur center with a mutant FNR protein enhances DNA binding.

Khoroshilova

Beinert

Kiley

1995

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

186

191

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In the facultative anaerobe Escherichia coli, the transcription factor FNR (fumarate nitrate reduction) regulates gene expression in response to oxygen deprivation. To investigate how the activity of FNR is regulated by oxygen availability, two mutant proteins, DA154 and LH28-DA154, which have enhanced in vivo activity in the presence of oxygen, were purified and compared. Unlike other previously exam-ined FNR preparations, the absorption spectrum of LH28-DA154 had two maxima at 324 nm and 419 nm, typical of iron-sulfur (Fe-S)-containing proteins. Consistent with these data, metal analysis showed that only the LH28-DA154 protein contained a significant amount of iron and acid-labile sulfide, and, by low temperature EPR spectroscopy, a signal typical of a [3Fe-4S] + cluster was detected. The protein that contained the Fe-S cluster also contained a higher proportion of dimers and had a 3-to 4-fold higher apparent affinity for the target DNA than the DA154 protein.In agreement with this, we found that when the LH28-DA154 protein was treated with an iron chelator (c,a'-dipyridyl), it lost its characteristic absorption and the apparent affinity for DNA was reduced 6-fold. However, increased DNA binding and the characteristic absorption spectrum could be restored by in vitro reconstitution of the Fe-S center. DNA binding of the LH28-DA154 protein was also affected by the redox state of the Fe-S center, since protein exposed to oxygen bound 1/10th as much DNA as the protein reduced anaerobically with dithionite. The observation that DNA binding is enhanced when the Fe-S center is reduced indicates that the redox state of the Fe-S center affects the DNA-binding activity of this protein and suggests a possible mechanism for regulation of the wild-type protein.A fundamental problem in biology is to understand the biochemical and molecular events that allow cells to sense and adapt to changes in oxygen in the environment. To address this problem, we have been studying how the activity of the Escherichia coli transcription factor FNR (fumarate nitrate reduction) is regulated by oxygen availability. In the absence of oxygen, FNR is converted to an active form that regulates the synthesis of many enzymes. A central question is to determine how FNR is converted to an active form.One region of FNR proposed to be required for regulation by oxygen is located near the N terminus and is characterized by a cluster of four closely spaced cysteine residues (16Cys-Xaa3-Cys-Xaa2-Cys-Xaa5-Cys29). Consistent with its supposed function as an oxygen regulatory site, this N-terminal region is located outside the regions of FNR that are similar to the DNA-binding and cAMP-binding domains of the well-studied, cAMP-dependent CAP protein (1). The FNR cysteine residues appear to be important components of the N-terminal region since mutational analysis has shown that three of the four cysteine residues (Cys-20, -23, -29) as well as one outside this region (Cys-122) are required for function (2).Several studies (3-8) suggest that iron is ...

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FNR‐dependent repression of the ndh gene of Escherichia coli and metal ion requirement for FNR‐regulated gene expression

Cited by 147 publications

References 35 publications

A role for iron in transcriptional activation by FNR

A role for iron in transcriptional activation by FNR

Two genetically-distinct and differentially-regulated aconitases (AcnA and AcnB) in Escherichia coli

Association of a polynuclear iron-sulfur center with a mutant FNR protein enhances DNA binding.

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