Surface signaling in transcriptional regulation of the ferric citrate transport system ofEscherichia coli: mutational analysis of the alternative sigma factor FecI supports its essential role infec transport gene transcription

Ochs, Martina M.; Angerer, Annemarie; Enz, Sabine; Braun, Volkmar

doi:10.1007/bf02174034

Cited by 30 publications

(38 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Neither the composition of the signals nor the process by which the signal is transmitted from FecA to FecR or from FecR to FecI has been elucidated. Binding of activated FecI to core RNA polymerase subsequently promotes transcription of the fecA operon by directing the holoenzyme to a promoter located immediately upstream of fecA (31). The result of this regulatory cascade is a ferric dicitrate-dependent induction of fecA and its accessory genes fecBCDE.…”

mentioning

confidence: 99%

Heme Utilization in Bordetella avium Is Regulated by RhuI, a Heme-Responsive Extracytoplasmic Function Sigma Factor

et al. 2001

View full text Add to dashboard Cite

Efficient utilization of heme as an iron (Fe) source by Bordetella avium requires bhuR, an Fe-regulated gene which encodes an outer membrane heme receptor. Upstream of bhuR is a 507-bp open reading frame, hereby designated rhuI (for regulator of heme uptake), which codes for a 19-kDa polypeptide. Whereas the 19-kDa polypeptide had homology to a subfamily of alternative sigma factors known as the extracytoplasmic function (ECF) sigma factors, it was hypothesized that rhuI encoded a potential in-trans regulator of the heme receptor gene in trans. Support for the model was strengthened by the identification of nucleotide sequences common to ECF sigma-dependent promoters in the region immediately upstream of bhuR. Experimental evidence for the regulatory activities of rhuI was first revealed by recombinant experiments in which overproduction of rhuI was correlated with a dramatically increased expression of BhuR. A putative rhuI-dependent bhuR promoter was identified in the 199-bp region located proximal to bhuR. When a transcriptional fusion of the 199-bp region and a promoterless lacZ gene was introduced into Escherichia coli, promoter activity was evident, but only when rhuI was coexpressed in the cell. Sigma competition experiments in E. coli demonstrated that rhuI conferred biological properties on the cell that were consistent with RhuI having sigma factor activity. Heme, hemoglobin, and several other heme-containing proteins were shown to be the extracellular inducers of the rhuI-dependent regulatory system. Fur titration assays indicated that expression of rhuI was probably Fur dependent.

show abstract

mentioning

confidence: 99%

Heme Utilization in Bordetella avium Is Regulated by RhuI, a Heme-Responsive Extracytoplasmic Function Sigma Factor

et al. 2001

View full text Add to dashboard Cite

show abstract

“…To examine a correlation between FecI activity and FecI binding to ␤Ј, previously isolated FecI point and deletion mutants (29,35) were tested for binding to ␤Ј. The K155E amino acid replacement in the predicted second helix of FecI reduced fecB-lacZ (Table 3).…”

Section: Resultsmentioning

confidence: 99%

“…In mutant FecI(K155E), mutated in the second predicted helix of region 4.2 (29), fecB-lacZ transcription was reduced to 10% of the wild-type level in ferric citrate-induced cells (35); as a LexA hybrid protein in combination with LexA-␤Ј, it repressed transcription of sulA-lacZ only to 30% of the wild-type FecI level. FecI(E141A) and FecI(K145E), which showed 91 and 99% of FecI wild-type fecB-lacZ transcription, respectively (35), repressed sulA-lacZ transcription to 78 and 104% of the wildtype FecI level, respectively. All of the FecI deletion mutants that are inactive as sigma factors (29) failed to interact with ␤Ј.…”

Section: Discussionmentioning

confidence: 99%

The FecI Extracytoplasmic-Function Sigma Factor of Escherichia coli Interacts with the β′ Subunit of RNA Polymerase

Mahren

Braun

2003

J Bacteriol

View full text Add to dashboard Cite

Transcription of the ferric citrate transport system of Escherichia coli K-12 is mediated by the extracytoplasmic-function (ECF) sigma factor FecI, which is activated by ferric citrate in the growth medium. By using a bacterial two-hybrid system, it was shown in vivo that FecI binds to the β′ subunit of RNA polymerase. The inactive mutant protein FecI(K155E) displayed reduced binding to β′, and small deletions along the entire FecI protein led to total impairment of β′ binding. In vitro, FecI was retained on Ni2+-nitrilotriacetic acid agarose loaded with a His-tagged β′1-313 fragment and coeluted with β′1-313. Binding of FecI to β′ and β′1-313 was enhanced by FecR1-85, which represents the cytoplasmic portion of the FecR protein that transmits the inducing signal across the cytoplasmic membrane. Interaction of FecR with FecI was demonstrated by showing that isolated FecR inhibited degradation of FecI by trypsin. This is the first demonstration of binding of an ECF sigma factor of the FecI type to the β′ subunit of RNA polymerase and of binding being enhanced by the protein that activates the ECF sigma factor.

show abstract

“…Binding of ferric citrate to the outer membrane FecA protein initiates a signal that is transmitted across the cytoplasmic membrane by FecR (15), resulting in an active FecI sigma factor that directs the RNA polymerase core enzyme to the promoter of the fecABCDE transport genes (1,6,22,23). The C-terminal domain of FecR ( Fig.…”

mentioning

confidence: 99%

Sites of Interaction between the FecA and FecR Signal Transduction Proteins of Ferric Citrate Transport in Escherichia coli K-12

et al. 2003

View full text Add to dashboard Cite

Transcription of the fecABCDE ferric citrate transport genes of Escherichia coli K-12 is initiated by a signaling cascade from the cell surface into the cytoplasm. FecR receives the signal in the periplasm from the outer membrane protein FecA loaded with ferric citrate, transmits the signal across the cytoplasmic membrane, and converts FecI in the cytoplasm to an active sigma factor. In this study, it was shown through the use of a bacterial two-hybrid system that, in the periplasm, the C-terminal FecR237-317 fragment interacts with the N-terminal FecA1-79 fragment. In the same C-terminal region, amino acid residues important for the interaction of FecR with FecA were identified by random and site-directed mutagenesis. They were preferentially located in and around a leucine motif (residues 247 to 268) which was found to be highly conserved in FecR-like proteins. The degree of residual binding of FecR mutant proteins to FecA was correlated with the degree of transcription initiation in response to ferric citrate in the culture medium. Three randomly generated inactive FecR mutants, FecR(L254E), FecR(L269G), and FecR(F284L), were suppressed to different degrees by the mutants FecA(G39R) and FecR(D43E). One FecR mutant, FecR (D138E, V197A), induced fecA promoter-directed transcription constitutively in the absence of ferric citrate and bound more strongly than wild-type FecR to FecA. The data showed that FecR interacts in the periplasm with FecA to confer ferric citrate-induced transcription of the fec transport genes and identified sites in FecR and FecA that are important for signal transduction

show abstract

Surface signaling in transcriptional regulation of the ferric citrate transport system ofEscherichia coli: mutational analysis of the alternative sigma factor FecI supports its essential role infec transport gene transcription

Cited by 30 publications

References 37 publications

Heme Utilization in Bordetella avium Is Regulated by RhuI, a Heme-Responsive Extracytoplasmic Function Sigma Factor

Heme Utilization in Bordetella avium Is Regulated by RhuI, a Heme-Responsive Extracytoplasmic Function Sigma Factor

The FecI Extracytoplasmic-Function Sigma Factor of Escherichia coli Interacts with the β′ Subunit of RNA Polymerase

Sites of Interaction between the FecA and FecR Signal Transduction Proteins of Ferric Citrate Transport in Escherichia coli K-12

Contact Info

Product

Resources

About