Mutants of Escherichia coli K12 Unable to use Fumarate as an Anaerobic Electron Acceptor

Lambden, Paul R.; Guest, John R.

doi:10.1099/00221287-97-2-145

Cited by 266 publications

(201 citation statements)

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“…The ability of the regulators to complement the JRG1728 fnr mutation was assessed by their capacity to restore anaerobic growth on leucine-supplemented glycerol nitrate agar (Lambden and Guest, 1976).…”

Section: Other Methodsmentioning

confidence: 99%

HlyX, the FNR homologue of Actinobacillus pleuropneumoniae, is a [4Fe–4S]‐containing oxygen‐responsive transcription regulator that anaerobically activates FNR‐dependent Class I promoters via an enhanced AR1 contact

Green

Baldwin

1997

Molecular Microbiology

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SummaryThe hlyX gene of the pig pathogen Actinobacillus pleuropneumoniae encodes HlyX, a homologue of FNR, the anaerobic transcription regulator of Escherichia coli. The hlyX gene complements the anaerobic respiratory deficiencies of E. coli fnr mutants but also induces the expression of an otherwise latent haemolysin. Therefore, FNR and HlyX have distinct but overlapping regulons. The hlyX gene has been overexpressed as a gst ::hlyX fusion and the HlyX protein purified. Similar to FNR, HlyX can acquire a [4Fe-4S] cluster, which promotes binding to the FNR box (K d of 20-30 nM) under anaerobic conditions. Expression of hlyX in E. coli induced the anaerobic production of at least five polypeptides, including the yfiD gene product, which were not induced by fnr. Analysis of the yfiD promoter region revealed the presence of two FNR boxes situated at ¹61.5 and ¹114.5. Consistent with this observation, expression from the semi-synthetic Class I promoter FFþ20pmelR was efficiently activated by HlyX but not by FNR. The weaker level of FNRmediated activation of Class I promoters suggests that there is a poorer activating contact (activating region 1 (AR1) equivalent) between FNR and RNA polymerase at these promoters and that HlyX possesses an additional or improved AR1. The AR1 of HlyX is partially characterized by a surface-exposed region around amino acid A187, which confers the altered specificity and provides an explanation for the existence of distinct but overlapping HlyX and FNR regulons.

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Section: Other Methodsmentioning

confidence: 99%

HlyX, the FNR homologue of Actinobacillus pleuropneumoniae, is a [4Fe–4S]‐containing oxygen‐responsive transcription regulator that anaerobically activates FNR‐dependent Class I promoters via an enhanced AR1 contact

Green

Baldwin

1997

Molecular Microbiology

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“…The operon is positively controlled by an activator protein encoded by the closely linked narL gene and responding to nitrate as the inducer (38,39). The narC operon is inducible only anaerobically, and its expression also depends on the pleiotropic activator protein encoded by fnr at minute 29 (6,23). Fumarate reductase is encoded by the frdABCD operon at minute 94 (8,9,12,21,24,36).…”

mentioning

confidence: 99%

“…Fumarate reductase is encoded by the frdABCD operon at minute 94 (8,9,12,21,24,36). The frd operon is induced anaerobically by fumarate in the absence of nitrate (7,13,16,21,23). Expression of the operon also depends on the Fnr protein (6,23).…”

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Molybdenum effector of fumarate reductase repression and nitrate reductase induction in Escherichia coli

Iuchi¹,

Lin²

1987

J Bacteriol

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In Escherichia coli the presence of nitrate prevents the utilization of fumarate as an anaerobic electron acceptor. The induction of the narC operon encoding the nitrate reductase is coupled to the repression of the frd operon encoding the fumarate reductase. This coupling is mediated by nitrate as an effector and the narL product as the regulatory protein (S. Iuchi and E. C. C. Lin, Proc. Natl. Acad. Sci. USA 84:3901-3905, 1987).The protein-ligand complex appears to control narC positively butfrd negatively. In the present study we found that a molybdenum coeffector acted synergistically with nitrate in the regulation of frd and narC. In chlD mutants believed to be impaired in molybdate transport (or processing), full repression of I(frd-lac) and full induction of @(narC-lac) by nitrate did not occur unlesshe growth medium was directly supplemented with molybdate (1 ,uM). This requirement was not clearly m*iifested in wild-type cells, apparently because it was met by the trace quantities of molybdate present as a contaminant in the mineral medium. In chLB mutants, which are known to accumulate the Mo cofactor because of its failure to be inserted as a prosthetic group into proteins such as nitrate reductase, nitrate repression of frd and induction of narC were also intensified by molybdate supplementation. In this case a deficiency of the molybdenum coeffector might have resulted from enhanced feedback inhibition of molybdate transport (or processing) by the elevated level of the unutilized Mo cofactor. In addition, mutations in chlE, which are known to block the synthesis of the organic moiety of the Mo cofactor, lowered the threshold concentrations of nitrate (<1 ,uM) necessary for frd repression and narC induction. These changes could be explained simply by the higher intracellular nitrate attainable in cells lacking the ability to destroy the effector.

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“…The anaerobic respiratory chains associated with these electron acceptors are generally inducible and are repressed during aerobic growth even in the presence of their inducer (for a general review see Ingledew & Poole, 1984). In addition, synthesis of the reductases (fumarate reductase, nitrate reductase and nitrite reductase) and other components of these respiratory systems depends on the regulatory locus fnr (Lambden & Guest, 1976;Newman & Cole, 1978;Chippaux et al, 1978). Evidence has accumulated to indicate that thefnr gene product (FNR) is a transcriptional activator which regulates the expression of its target genes in response to anaerobiosis.…”

Section: Introductionmentioning

confidence: 99%

Regulation and Over-expression of the fnr Gene of Escherichia coli

1987

Self Cite

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3279The fnr gene of Escherichia coli encodes a transcriptional activator (FNR) which is required for the expression of a number of genes involved in anaerobic respiratory pathways. From the study of a translational fusion of fnr to the gene for /3-galactosidase (ZacZ) it has been concluded that the fnr gene is expressed under both aerobic and anaerobic conditions and is subject to autoregulation and repression by glucose, particularly during anaerobic growth. These findings imply that during anaerobiosis the FNR protein adopts an active conformation, in which it functions both as a repressor of'the fnr gene and as an activator offitr-dependent genes. Sequences in the 5' non-coding region of fnr which could be involved in autoregulation are discussed. The fnr coding region was cloned into an expression vector which has allowed an amplification of FNR synthesis such that it accounts for about 2% of total cell protein. The ability to over-produce FNR in this way should be very useful for future biochemical studies.

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Mutants of Escherichia coli K12 Unable to use Fumarate as an Anaerobic Electron Acceptor

Cited by 266 publications

References 29 publications

HlyX, the FNR homologue of Actinobacillus pleuropneumoniae, is a [4Fe–4S]‐containing oxygen‐responsive transcription regulator that anaerobically activates FNR‐dependent Class I promoters via an enhanced AR1 contact

HlyX, the FNR homologue of Actinobacillus pleuropneumoniae, is a [4Fe–4S]‐containing oxygen‐responsive transcription regulator that anaerobically activates FNR‐dependent Class I promoters via an enhanced AR1 contact

Molybdenum effector of fumarate reductase repression and nitrate reductase induction in Escherichia coli

Regulation and Over-expression of the fnr Gene of Escherichia coli

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