Two-Component Systems in
            <i>Haemophilus influenzae</i>
            : a Regulatory Role for ArcA in Serum Resistance

Souza-Hart, J. A. De; Blackstock, Walter; Modugno, V. Di; Holland, I. B.; Kok, Menno

doi:10.1128/iai.71.1.163-172.2003

Cited by 50 publications

(46 citation statements)

References 58 publications

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“…One possible candidate, the global regulator ArcA has recently been linked to virulence in Haemophilus influenzae and Vibrio cholerae (23,27). ArcA has not been characterized in A. pleuropneumoniae; however, genomic sequence data available for A. pleuropneumoniae at http://www .ncbi.nlm.nih.gov/sutils/genom_table.cgi?…”

Section: Discussionmentioning

confidence: 99%

Deletion of the Anaerobic Regulator HlyX Causes Reduced Colonization and Persistence ofActinobacillus pleuropneumoniaein the Porcine Respiratory Tract

et al. 2005

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Actinobacillus pleuropneumoniae, the etiological agent of porcine pleuropneumonia, is able to persist on respiratory epithelia, in tonsils, and in the anaerobic environment of encapsulated lung sequesters. We have demonstrated previously that putative HlyX-regulated genes, coding for dimethyl sulfoxide (DMSO) reductase and aspartate ammonia lyase, are upregulated during infection and that deletions in these genes result in attenuation of the organism. The study presented here investigates the role of HlyX, the fumarate nitrate reductase regulator (FNR) homologue of A. pleuropneumoniae. By constructing an isogenic A. pleuropneumoniae hlyX mutant, the HlyX protein is shown to be responsible for upregulated expression of both DMSO reductase and aspartate ammonia lyase (AspA) under anaerobic conditions. In a challenge experiment the A. pleuropneumoniae hlyX mutant is shown to be highly attenuated, unable to persist in healthy lung epithelium and tonsils, and impaired in survival inside sequestered lung tissue. Further, using an A. pleuropneumoniae strain carrying the luxAB genes as transcriptional fusion to aspA on the chromosome, the airway antioxidant glutathione was identified as one factor potentially responsible for inducing HlyX-dependent gene expression of A. pleuropneumoniae in epithelial lining fluid.Actinobacillus pleuropneumoniae, the etiological agent of porcine pleuropneumonia (10), is able to persist in host tissues, such as tonsillar crypts and sequestered necrotic lung, where the oxygen supply is scarce. The resulting carrier animals are the major source of infection for previously A. pleuropneumoniae-free herds (10) and, therefore, unraveling the mechanisms of persistence is highly relevant to effective vaccination and control of the infection.In Escherichia coli a number of genes expressed under anaerobic conditions are regulated by the global regulator FNR (for fumarate nitrate reductase regulator) (24). An A. pleuropneumoniae FNR homologue, HlyX, has been found to induce hemolytic activity in E. coli under anoxic conditions and to be able to complement E. coli fnr deletions (18, 26). Like FNR, HlyX contains four iron-sulfur clusters responsible for the DNA-binding ability of the protein (12).In A. pleuropneumoniae, anaerobically regulated genes appear to play a role in virulence and persistence. We have shown previously that A. pleuropneumoniae genes upregulated under anaerobic conditions in culture are not only upregulated in sequestered necrotic lung tissue where anoxic conditions are to be expected (1) but also upon the supplementation of culture medium with bronchoalveolar lavage fluid from A. pleuropneumoniae-infected pigs, which mimics conditions as they occur on respiratory epithelium (1-3, 15). Further, we have shown that isogenic mutants lacking aspartate ammonia lyase (aspartase) activity or both dimethyl sulfoxide (DMSO) reductase and aspartase activity were reduced in virulence and in their ability to persist on unaltered respiratory epithelium (2, 15).Since both the DMSO reductase (d...

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Section: Discussionmentioning

confidence: 99%

Deletion of the Anaerobic Regulator HlyX Causes Reduced Colonization and Persistence ofActinobacillus pleuropneumoniaein the Porcine Respiratory Tract

et al. 2005

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“…16 ArcA, like the majority of RRs, is a transcription factor that, in addition to its N-terminal regulatory domain, contains a C-terminal helix-turn-helix DNA-binding domain. In recent years the ArcA-ArcB TCS has been implicated in the direct or indirect regulation of virulence and resistance in a number of clinically important human pathogens including Salmonella enterica serovar Enteritidis, 17 Haemophilus influenzae 18 and Vibrio cholerae. 19 ArcA is a member of the OmpR/PhoB subfamily of RR transcription factors, by far the largest subfamily of RRs, accounting for 15 of the 34 RRs presently identified in E. coli.…”

Section: Introductionmentioning

confidence: 99%

Structural Analysis and Solution Studies of the Activated Regulatory Domain of the Response Regulator ArcA: A Symmetric Dimer Mediated by the α4-β5-α5 Face

Toro-Roman

Mack²,

Stock

2005

Journal of Molecular Biology

119

137

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SUMMARYEscherichia coli react to changes from aerobic to anaerobic conditions of growth using the ArcAArcB two-component signal transduction system. This system, in conjunction with other proteins, regulates the respiratory metabolic pathways in the organism. ArcA is a member of the OmpR/ PhoB subfamily of response regulator transcription factors that are known to regulate transcription by binding in tandem to target DNA direct repeats. It is still unclear in this subfamily how activation by phosphorylation of the regulatory domain of response regulators stimulates DNA binding by the effector domain and how dimerization and domain orientation, as well as intra-and intermolecular interactions, affect this process. In order to address these questions we have solved the crystal structure of the regulatory domain of ArcA in the presence and absence of the phosphoryl analog, BeF 3 − . In the crystal structures, the regulatory domain of ArcA forms a symmetric dimer mediated by the α4-β5-α5 face of the protein and involving a number of residues that are highly conserved in the OmpR/PhoB subfamily. It is hypothesized that members of this subfamily use a common mechanism of regulation by dimerization. Additional biophysical studies were employed to probe the oligomerization state of ArcA, as well as its individual domains, in solution. The solution studies show the propensity of the individual domains to associate into oligomers larger than the dimer observed for the intact protein, and suggest that the C-terminal DNA-binding domain also plays a role in oligomerization.

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“…While over 31 TCST systems have been identified in Escherichia coli and 13 in Streptococcus pneumoniae (83,90), only four have been identified in H. influenzae genome sequences (27,39). The identified NTHI TCST systems are orthologs to ArcAB (senses redox conditions) (22,85,86), NarPQ (senses nitrate-nitrite levels) (76), PhoBR (senses phosphate levels), and QseBC (senses quorum-sensing signals). To date, there are no published reports on the role of PhoBR and QseBC in H. influenzae.…”

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confidence: 99%

Characterization of a Ferrous Iron-Responsive Two-Component System in Nontypeable Haemophilus influenzae

et al. 2012

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Nontypeable Haemophilus influenzae (NTHI), an opportunistic pathogen that is commonly found in the human upper respiratory tract, has only four identified two-component signal transduction systems. One of these, an ortholog to the QseBC (quorum-sensing Escherichia coli) system, was characterized. This system, designated firRS, was found to be transcribed in an operon with a gene encoding a small, predicted periplasmic protein with an unknown function, ygiW. The ygiW-firRS operon exhibited a unique feature with an attenuator present between ygiW and firR that caused the ygiW transcript level to be 6-fold higher than the ygiW-firRS transcript level. FirRS induced expression of ygiW and firR, demonstrating that FirR is an autoactivator. Unlike the QseBC system of E. coli, FirRS does not respond to epinephrine or norepinephrine. FirRS signal transduction was stimulated when NTHI cultures were exposed to ferrous iron or zinc but was unresponsive to ferric iron. Notably, the ferrous iron-responsive activation only occurred when a putative iron-binding site in FirS and the key phosphorylation aspartate in FirR were intact. FirRS was also activated when cultures were exposed to cold shock. Mutants in ygiW, firR, and firS were attenuated during pulmonary infection, but not otitis media. These data demonstrate that the H. influenzae strain 2019 FirRS is a two-component regulatory system that senses ferrous iron and autoregulates its own operon.

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Two-Component Systems in Haemophilus influenzae : a Regulatory Role for ArcA in Serum Resistance

Cited by 50 publications

References 58 publications

Deletion of the Anaerobic Regulator HlyX Causes Reduced Colonization and Persistence ofActinobacillus pleuropneumoniaein the Porcine Respiratory Tract

Deletion of the Anaerobic Regulator HlyX Causes Reduced Colonization and Persistence ofActinobacillus pleuropneumoniaein the Porcine Respiratory Tract

Structural Analysis and Solution Studies of the Activated Regulatory Domain of the Response Regulator ArcA: A Symmetric Dimer Mediated by the α4-β5-α5 Face

Characterization of a Ferrous Iron-Responsive Two-Component System in Nontypeable Haemophilus influenzae

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