Regulation of citrate‐dependent iron transport of <i>Escherichia coli</i>: FecR is required for transcription activation by Feel

Ochs, Martina M.; Veitinger, S; Kim, InSook; Weiz, Dietrich; Angerer, Annemarie; Braun, Volkmar

doi:10.1111/j.1365-2958.1995.tb02226.x

Cited by 103 publications

(145 citation statements)

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“…atu3692 encodes a putative sigma factor that shows the most similarity with sigma factors involved in iron-dependent regulation of siderophore biosynthesis in Pseudomonas spp., including PbrA from P. fluorescens M114 (Venturi et al, 1995), PfrI from P. putida WCS358 (Sexton et al, 1995), and PvdS from P. aeruginosa (Ochsner et al, 1995). Finally, atu3693 encodes a protein with similarity to FecR, also involved in iron-mediated gene regulation (Braun et al, 2003;Ochs et al, 1995). The presence of these genes adjacent to the ATS gene cluster supports our hypothesis that this gene cluster encodes the biosynthesis of a siderophore.…”

Section: Structure Of the Ats Gene Clustersupporting

confidence: 64%

Identification and analysis of a siderophore biosynthetic gene cluster from Agrobacterium tumefaciens C58

2004

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Using the complete genome sequence from Agrobacterium tumefaciens C58, the authors identified a secondary metabolite gene cluster that encodes the biosynthesis of a metabolite with siderophore activity. Support for this conclusion came from genetic and regulatory analysis of the gene cluster, along with the purification of a metabolite from A. tumefaciens C58 with iron-chelating activity. Genetic analysis of mutant strains disrupted in this gene cluster showed that these strains grew more slowly than the wild-type strain in medium lacking iron. Additionally, the mutant strains failed to produce a chrome-azurol-S-reactive material in liquid or solid medium, and failed to produce the metabolite with iron-chelating characteristics that was identified in the wild-type strain. Addition of this purified metabolite to the growth medium of a mutant strain restored its ability to grow in iron-deficient medium. Furthermore, expression of this gene cluster was induced by growth under iron-limiting conditions, suggesting that expression of this gene cluster occurs when iron is scarce. These data are all consistent with the proposal that the proteins encoded by this gene cluster are involved in the production of a siderophore. Interestingly, these proteins show the highest level of amino acid similarity to proteins from a gene cluster found in the filamentous cyanobacterium Nostoc sp. PCC7120, rather than to known siderophore biosynthetic enzymes. Given these properties, it is proposed that the siderophore produced by A. tumefaciens C58 will have a unique chemical structure. Production of the siderophore was not required for virulence of A. tumefaciens when tested with a standard stem inoculation assay.

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Section: Structure Of the Ats Gene Clustersupporting

confidence: 64%

Identification and analysis of a siderophore biosynthetic gene cluster from Agrobacterium tumefaciens C58

2004

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“…sigX and its downstream gene rsiX (encoding the anti-X factor) were originally observed to be homologous (but not orthologous) to Escherichia coli fecI and fecR, which are involved in expression of ferric citrate transport genes (37). Although expression of sigX in E. coli can complement a fecI mutant (4), the B. subtilis sigX mutant is not affected in any known ferri-siderophore uptake systems (20).…”

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confidence: 99%

The Bacillus subtilis Extracytoplasmic-Function σ ^X Factor Regulates Modification of the Cell Envelope and Resistance to Cationic Antimicrobial Peptides

2004

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Bacillus subtilis contains seven extracytoplasmic-function factors that activate partially overlapping regulons. We here identify four additional members of the X regulon, pbpX (penicillin-binding protein), ywnJ, the dlt operon (D-alanylation of teichoic acids), and the pss ybfM psd operon (phosphatidylethanolamine biosynthesis). Modification of teichoic acids by esterification with D-alanine and incorporation of phosphatidylethanolamine into the cell membrane have a common consequence: in both cases positively charged amino groups are introduced into the cell envelope. The resulting reduction in the net negative charge of the cell envelope has been previously implicated as a resistance mechanism specific for cationic antimicrobial peptides. Consistent with this notion, we find that both sigX and dltA mutants are more sensitive to nisin than wild-type cells. We conclude that activation of the X regulon serves to alter cell surface properties to provide protection against antimicrobial peptides.Bacillus subtilis encodes seven extracytoplasmic-function (ECF) factors. Most studies to date have focused on three:X , W , and M (reviewed in reference 19). sigX and its downstream gene rsiX (encoding the anti-X factor) were originally observed to be homologous (but not orthologous) to Escherichia coli fecI and fecR, which are involved in expression of ferric citrate transport genes (37). Although expression of sigX in E. coli can complement a fecI mutant (4), the B. subtilis sigX mutant is not affected in any known ferri-siderophore uptake systems (20).To understand the function of X , we identified several X -regulated genes using a consensus promoter search method (22). In these initial studies, we characterized six genes that are preceded by promoters recognized by X : sigX, abh (an AbrB homolog), csbB (a membrane-bound glucosyl transferase) (2), divIC (a membrane-bound cell-division initiation protein), lytR (a negative regulator of autolysin) (30), and rapD (a response regulator aspartate phosphatase) (43). These results suggested that X modulates aspects of cell envelope metabolism. Interestingly, most X -controlled genes are also transcribed by other forms of holoenzyme. For example, csbB has an additional B -dependent promoter, lytR and rapD both have additional A -dependent promoters, and sigX itself is preferentially transcribed from an upstream A -dependent site in addition to the X -dependent autoregulatory promoter (20,22). Moreover, in some cases (e.g., abh and divIC) the promoter activated by the E X holoenzyme can also be recognized by the E W holoenzyme at least in vitro (21). Similarly, the recently defined bcrC gene (a bacitracin resistance gene) is transcribed from a promoter that is recognized by either X or M (7, 38). The unknown function of many X -controlled genes makes it difficult to predict a phenotype for the sigX mutant. This challenge is exacerbated by the fact that many of the genes are expressed from multiple promoters or by multiple holoenzyme forms activating the same promoter. The latte...

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“…(Fe 3ϩ citrate) 2 binds to the outer membrane protein FecA and without further transport into the cell induces transcription of the fec transport genes (9,14). The signal transmitted by FecA loaded with (Fe 3ϩ citrate) 2 across the outer membrane is transmitted across the cytoplasmic membrane by FecR, a transmembrane protein (21,28) that interacts with FecA in the periplasm and with the FecI extracytoplasmic-function (ECF) factor in the cytoplasm (7,8,18,24). FecR enables FecI to bind to the RNA polymerase core enzyme; this complex then binds to the fecA promoter to initiate transcription of the fec transport genes (1,2).…”

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Analysis of the Ferric Citrate Transport Gene Promoter of Escherichia coli

Enz

Mahren²,

Menzel³

et al. 2003

J Bacteriol

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FecI, an extracytoplasmic-function factor, is required for initiation of transcription of the ferric citrate transport genes. A mutational analysis of the fecA promoter revealed that the nonconserved ؊10 region and a downstream regulatory element are important for fecA promoter activity. However, nucleotide substitutions in the well-conserved ؊35 region also have an effect on the fecA promoter activity. Titration of FecI suggests that the FecI-RNA polymerase holoenzyme does not bind strongly to the downstream regulatory element, which is therefore probably involved in a subsequent step of transcription initiation.In Escherichia coli, transcription of the ferric citrate transport genes fecABCDE is controlled by a signal transduction mechanism that starts at the cell surface. (Fe 3ϩ citrate) 2 binds to the outer membrane protein FecA and without further transport into the cell induces transcription of the fec transport genes (9, 14). The signal transmitted by FecA loaded with (Fe 3ϩ citrate) 2 across the outer membrane is transmitted across the cytoplasmic membrane by FecR, a transmembrane protein (21, 28) that interacts with FecA in the periplasm and with the FecI extracytoplasmic-function (ECF) factor in the cytoplasm (7,8,18,24). FecR enables FecI to bind to the RNA polymerase core enzyme; this complex then binds to the fecA promoter to initiate transcription of the fec transport genes (1, 2). The only promoter known to be recognized by FecI is that of the fecABCDE operon; no other factor of E. coli is endowed with such a narrow promoter specificity (17).ECF factors belong to a subfamily of the 70 class, based on their sequence conservation and function across bacterial species (3,10,16,20). Comparisons of sequences indicate that the genomes of Caulobacter crescentus, Pseudomonas aeruginosa, Nitrosomonas europaea, and Streptomyces coelicolor are particularly rich in ECF factors and contain 13, 19, 22, and 50 predicted ECF factors, respectively. factors share four conserved regions which can be further subdivided. Region 4.2 recognizes the Ϫ35 element, and region 2.4 recognizes the Ϫ10 element of promoter DNA. A bacterial promoter consists of at least about 60 bp spanning the positions Ϫ40 to ϩ20 in relation to the ϩ1 start site of transcription (12). A comparison of ECF factors reveals that the Ϫ35 sequence and the spacing but not the sequence between the Ϫ35 and Ϫ10 regions are well conserved (Table 1) (4,5,10,11,19,20,23,29). The Ϫ10 sequences show less homology (Table 1), which is reflected by the low homology of regions 2.4 in the ECF factors (16). The characteristic feature of region 2.4 of 70 , a set of hydrophobic residues that form an amphipatic ␣-helix, is not present in the corresponding region of ECF factors (16). The diversity of the Ϫ10 sequences and region 2.4 probably accounts for the coexistence of multiple members of the ECF -factor subfamily in the same species.Previously, it was shown that transcription of the fec transport genes starts at nucleotide 2741 (7) of the fec sequence (22), resulti...

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Regulation of citrate‐dependent iron transport of Escherichia coli: FecR is required for transcription activation by Feel

Cited by 103 publications

References 31 publications

Identification and analysis of a siderophore biosynthetic gene cluster from Agrobacterium tumefaciens C58

Identification and analysis of a siderophore biosynthetic gene cluster from Agrobacterium tumefaciens C58

The Bacillus subtilis Extracytoplasmic-Function σ ^X Factor Regulates Modification of the Cell Envelope and Resistance to Cationic Antimicrobial Peptides

Analysis of the Ferric Citrate Transport Gene Promoter of Escherichia coli

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Regulation of citrate‐dependent iron transport of Escherichia coli: FecR is required for transcription activation by Feel

Cited by 103 publications

References 31 publications

Identification and analysis of a siderophore biosynthetic gene cluster from Agrobacterium tumefaciens C58

Identification and analysis of a siderophore biosynthetic gene cluster from Agrobacterium tumefaciens C58

The Bacillus subtilis Extracytoplasmic-Function σ X Factor Regulates Modification of the Cell Envelope and Resistance to Cationic Antimicrobial Peptides

Analysis of the Ferric Citrate Transport Gene Promoter of Escherichia coli

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The Bacillus subtilis Extracytoplasmic-Function σ ^X Factor Regulates Modification of the Cell Envelope and Resistance to Cationic Antimicrobial Peptides