Surface Signaling in Ferric Citrate Transport Gene Induction: Interaction of the FecA, FecR, and FecI Regulatory Proteins

Enz, Sabine; Mahren, Susanne; Stroeher, Uwe H.; Braun, Volkmar

doi:10.1128/jb.182.3.637-646.2000

Cited by 110 publications

(116 citation statements)

References 26 publications

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“…6). It has been shown that in the Fec system, FecA and FecI both interact physically with FecR (46). Interactions between the protein components of the FpvA͞FpvR͞ PvdS pathway have not yet been demonstrated.…”

Section: Discussionmentioning

confidence: 99%

Siderophore-mediated signaling regulates virulence factor production in Pseudomonas aeruginosa

Lamont

Beare

Ochsner

et al. 2002

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

509

501

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Numerous bacteria secrete low molecular weight compounds termed siderophores that have a high affinity for iron ions. Siderophores have a well-documented role as iron-scavenging chemicals, chelating iron ions in the environment whereupon the ferrisiderophores reenter the bacterial cells by means of specific cell-surface receptors. The iron is then released for incorporation into bacterial proteins. Here we show that in addition to its role as an iron-scavenger, the siderophore pyoverdine that is secreted by Pseudomonas aeruginosa regulates the production of at least three virulence factors (exotoxin A, an endoprotease, and pyoverdine itself), which are major contributors to the ability of this bacterium to cause disease. Regulation occurs through a transmembrane signaling system that includes an outer membrane receptor for ferripyoverdine, a signal-transducing protein that is predicted to extend from the periplasm into the cytoplasm, and a sigma factor. Expression of genes that form part of the regulon is triggered by pyoverdine so that this siderophore acts as a signaling molecule to control the production of secreted products. Recognition that a siderophore acts as a signaling molecule has important implications for the understanding of interactions between bacterial cells.

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Section: Discussionmentioning

confidence: 99%

Siderophore-mediated signaling regulates virulence factor production in Pseudomonas aeruginosa

Lamont

Beare

Ochsner

et al. 2002

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

509

501

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“…Deletion of the N terminus abolishes induction, but transport is fully retained (28). FecR interacts with the FecI sigma factor in the cytoplasm and controls transcription initiation of the fec transport genes (18,43). Comparisons with genome sequences of other bacteria reveal homologs of FecIRA whose encoding genes are arranged in the same order as fecIRA of E. coli (7).…”

mentioning

confidence: 99%

Defined Inactive FecA Derivatives Mutated in Functional Domains of the Outer Membrane Transport and Signaling Protein of Escherichia coli K-12

Sauter

Braun

2004

J Bacteriol

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The FecA outer membrane protein of Escherichia coli functions as a transporter of ferric citrate and as a signal receiver and signal transmitter for transcription initiation of the fec transport genes. Three FecA regions for which functional roles have been predicted from the crystal structures were mutagenized: (i) loops 7 and 8, which move upon binding of ferric citrate and close the entrance to the ferric citrate binding site; (ii) the dinuclear ferric citrate binding site; and (iii) the interface between the globular domain and the ␤-barrel. Deletion of loops 7 and 8 abolished FecA transport and induction activities. Deletion of loops 3 and 11 also inactivated FecA, whereas deletion of loops 9 and 10 largely retained FecA activities. The replacement of arginine residue R365 or R380 and glutamine Q570, which are predicted to serve as binding sites for the negatively charged dinuclear ferric citrate, with alanine resulted in inactive FecA, whereas the binding site mutant R438A retained approximately 50% of the FecA induction and transport activities. Residues R150, E541, and E587, conserved among energy-coupled outer membrane transporters, are predicted to form salt bridges between the globular domain and the ␤-barrel and to contribute to the fixation of the globular domain inside the ␤-barrel. Mutations E541A and E541R affected FecA induction and transport activity slightly, whereas mutations E587A and E587R more strongly reduced FecA activity. The double mutations R150A E541R and R150A E587R nearly abolished FecA activity. Apparently, the salt bridges are less important than the individual functions these residues seem to have for FecA activity. Comparison of the properties of the FecA, FhuA, FepA, and BtuB transporters indicates that although they have very similar crystal structures, the details of their functional mechanisms differ.

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“…Binding Assays Using Immobilized HrcA114 -To demonstrate interactions between HrcA and GroEL, we analyzed binding of GroEL to immobilized HrcA114 following the method described by Enz and coworkers (24). Two Ni-NTA-agarose columns were prepared, one loaded with His 6 -HrcA114 and the other left without protein.…”

Section: Bacterial Strains and Plasmids And Growthmentioning

confidence: 99%

Isolation and Analysis of Mutant Alleles of the Bacillus subtilis HrcA Repressor with Reduced Dependency on GroE Function

Reischl

Wiegert

Schumann

2002

Journal of Biological Chemistry

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The hrcA gene of Bacillus subtilis codes for a transcriptional repressor protein that negatively regulates expression of the heptacistronic dnaK and the bicistronic groE operon by binding to an operator-element called CIRCE. Recently, we have published data suggesting that the activity of HrcA is modulated by the GroE chaperonin system. Biochemical analyses of the HrcA protein have been hampered so far by its strong tendency to aggregate. Here, a genetic method was used to isolate mutant forms of HrcA with increased activity under conditions of decreased GroE function. One of these mutant forms (HrcA114) containing five amino acid replacements exhibited enhanced solubility when overexpressed. HrcA114 purified under native conditions produced two retarded CIRCE-containing DNA fragments in band shift experiments. The amount of the larger fragment increased after addition of GroEL, GroES, and ATP but decreased when ATP was replaced by the nonhydrolyzable ATP analog ATP␥S. DNase I footprinting experiments exhibited full protection of the CIRCE element and neighboring nucleotides in an asymmetric way. An in vitro binding assay using affinity chromatography showed direct and specific interaction between HrcA114 and GroEL. All these experimental data are in full agreement with our previously published model that HrcA needs the GroE chaperonin system for activation.Bacteria encode genetic systems allowing them to adapt to many stressful situations, including high and low temperature, hyperosmotic and oxidative stress, and severe DNA damage (1). The best-studied stress response is the so-called heat shock response, which is induced after a sudden increase in temperature. This response is characterized by the transiently enhanced synthesis of a group of proteins collectively known as heat shock proteins encoded by heat shock genes. Work carried out over the last 5 years has revealed that in most eubacteria heat shock genes are organized in two and more regulons, where each regulon is either under positive control of an alternative sigma factor or under negative control of a transcriptional repressor (2-5).In Bacillus subtilis, three different regulons have been identified so far, where Class I heat shock genes are under the negative control of the HrcA transcriptional repressor. This protein binds to an operator designated CIRCE 1 (Controlling Inverted Repeat of Chaperone Expression) (6), which precedes the heptacistronic dnaK and the bicistronic groE operon (7-9). Upon a heat shock, HrcA dissociates from its operators leading to a transient induction of the two operons followed by rebinding after about 10 min (7,8,10). The pertinent question concerning all heat shock regulators is how the activity of these proteins is modulated after a heat shock. In the present case, we have presented data suggesting that the activity of HrcA is modulated by the GroE chaperonin system (11). HrcA is maintained in an active conformation able to bind to CIRCE through GroE. Under conditions of increased formation of nonnative proteins in th...

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Surface Signaling in Ferric Citrate Transport Gene Induction: Interaction of the FecA, FecR, and FecI Regulatory Proteins

Cited by 110 publications

References 26 publications

Siderophore-mediated signaling regulates virulence factor production in Pseudomonas aeruginosa

Siderophore-mediated signaling regulates virulence factor production in Pseudomonas aeruginosa

Defined Inactive FecA Derivatives Mutated in Functional Domains of the Outer Membrane Transport and Signaling Protein of Escherichia coli K-12

Isolation and Analysis of Mutant Alleles of the Bacillus subtilis HrcA Repressor with Reduced Dependency on GroE Function

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