Article

NssR, a member of the Crp-Fnr superfamily from Campylobacter jejuni, regulates a nitrosative stress-responsive regulon that includes both a single-domain and a truncated haemoglobin

School of Biomedical and Molecular Sciences, University of Surrey, Guildford GU2 7XH, UK.
Molecular Microbiology (Impact Factor: 5.03). 09/2005; 57(3):735-50. DOI: 10.1111/j.1365-2958.2005.04723.x
Source: PubMed

ABSTRACT Consistent with its role as a nitric oxide (NO)-detoxifying globin in Campylobacter jejuni, Cgb (Campylobacter globin) expression is strongly and specifically induced following exposure to nitrosative stress, suggesting a previously unrecognized capacity for NO-related stress sensing in this food-borne pathogen. In this study, Fur and PerR have been eliminated as major regulators of cgb, and NssR (Cj0466), a member of the Crp-Fnr superfamily, has been identified as the major positive regulatory factor that controls nitrosative stress-responsive expression of this gene. Accordingly, disruption of nssR resulted in the abolition of inducible cgb expression, which was restored by a complementing chromosomal insertion of the wild-type gene with its indigenous promoter at a second location. The NssR-deficient mutant was more sensitive to NO-related stress than a cgb mutant and this phenotype most likely arises from the failure of these cells to induce other NO-responsive components in addition to Cgb. Indeed, analysis of global gene expression, by microarray and confirmatory real-time polymerase chain reaction (PCR) in the wild type and nssR mutant, not only confirmed the dependence of inducible cgb expression on NssR, but also revealed for the first time a novel NssR-dependent nitrosative stress-responsive regulon. This regulon of at least four genes includes Cj0465c, a truncated globin. Consistent with NssR being a Crp-Fnr superfamily member, an Fnr-like binding sequence (TTAAC-N(4)-GTTAA) was found upstream of each gene at locations -40.5 to -42.5 relative to the centre of the binding sites and the transcription start point. Site-directed mutagenesis confirmed that this cis-acting motif mediates the nitrosative stress-inducible expression of cgb.

Download full-text

Full-text

Available from: Gemma L Marsden, Nov 05, 2014
0 Followers
 · 
95 Views
  • Source
    • "cjsa_0012 (cj0012c; rrc) encodes a protein which protects anaerobic microorganisms against oxidative stress (Yamasaki et al. 2004). cjsa_1497 (cj1586; cgb) encodes a hemoglobin which oxidizes and detoxifies nitric oxide against nitrosative stress (Elvers et al. 2005). fdxA (encoding a [Fe–S] protein) is involved in the oxidative stress defense of C. jejuni (van Vliet et al. 2001), but the functions of fdxB (encoding a [Fe-S] protein) and cjsa_0823 (cj0874c; encoding a putative cytochrome C) remain unknown . "
    [Show abstract] [Hide abstract]
    ABSTRACT: Campylobacter jejuni clone SA recently emerged as the predominant cause of sheep abortion in the U.S. and is also associated with foodborne gastroenteritis in humans. A distinct phenotype of this clone is its ability to induce bacteremia and abortion. To facilitate understanding the pathogenesis of this hypervirulent clone, we analyzed a clinical isolate (IA3902) of clone SA using multi-omics approaches. The genome of IA3902 contains a circular chromosome of 1,635,045 bp and a circular plasmid of 37,174 bp. Comparative genomic analysis revealed that IA3902 is most closely related to C. jejuni NCTC11168, which is a reference strain and was previously shown to be non-abortifacient in pregnant animals. Despite the high genomic synteny and sequence homology, there are 12 variable regions and 8696 SNPs and indels between the two genomes. Notably, the variable genes in the capsular polysaccharides biosynthesis and O-linked glycosylation loci of IA3902 are highly homogenous to their counterparts in C. jejuni subsp. doylei and C. jejuni G1, which are known to be frequently associated with bacteremia. Transcriptomic and proteomic profiles were conducted to compare IA3902 with NCTC11168, which revealed that the pathways of energy generation, motility, and serine utilization were significantly up-regulated in IA3902, while the pathways of iron uptake and proline, glutamate, aspartate and lactate utilization were significantly down-regulated. These results suggest C. jejuni clone SA has evolved distinct genomic content and gene expression patterns that modulate surfacce polysacharide structures, motilitiy and metabolic pathways. These changes may have contributed to its hyper virulence in abortion induction.
    Genome Biology and Evolution 11/2013; 5(11). DOI:10.1093/gbe/evt172 · 4.53 Impact Factor
  • Source
    • "Another transcription factor belonging to the E subgroup of the CRP/FNR superfamily, i.e. NssR from Campylobacter jejuni, has been recently described to act, perhaps indirectly, as a NO sensor (Elvers et al., 2005). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Pseudomonas aeruginosa is a well-known pathogen in chronic respiratory diseases such as cystic fibrosis. Infectivity of P. aeruginosa is related to the ability to grow under oxygen-limited conditions using the anaerobic metabolism of denitrification, in which nitrate is reduced to dinitrogen via nitric oxide (NO). Denitrification is activated by a cascade of redox-sensitive transcription factors, among which is the DNR regulator, sensitive to nitrogen oxides. To gain further insight into the mechanism of NO-sensing by DNR, we have developed an Escherichia coli-based reporter system to investigate different aspects of DNR activity. In E. coli DNR responds to NO, as shown by its ability to transactivate the P. aeruginosa norCB promoter. The direct binding of DNR to the target DNA is required, since mutations in the helix-turn-helix domain of DNR and specific nucleotide substitutions in the consensus sequence of the norCB promoter abolish the transcriptional activity. Using an E. coli strain deficient in haem biosynthesis, we have also confirmed that haem is required in vivo for the NO-dependent DNR activity, in agreement with the property of DNR to bind haem in vitro. Finally, we have shown, we believe for the first time, that DNR is able to discriminate in vivo between different diatomic signal molecules, NO and CO, both ligands of the reduced haem iron in vitro, suggesting that DNR responds specifically to NO.
    Microbiology 06/2009; 155(Pt 9):2838-44. DOI:10.1099/mic.0.028027-0 · 2.84 Impact Factor
  • Source
    • "In C. jejuni, Hmp and NorV are absent but there is a single domain globin (Cgb), which has been shown to protect against nitrosative stress (Elvers et al., 2004). In keeping with this, Cgb is inducible by nitrosative stress via the regulatory protein NssR (Elvers et al., 2005). The role of other enzymes, including NrfA, in NO defence in C. jejuni is unknown. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Pathways of electron transport to periplasmic nitrate (NapA) and nitrite (NrfA) reductases have been investigated in Campylobacter jejuni, a microaerophilic food-borne pathogen. The nap operon is unusual in lacking napC (encoding a tetra-haem c-type cytochrome) and napF, but contains a novel gene of unknown function, napL. The iron-sulphur protein NapG has a major role in electron transfer to the NapAB complex, but we show that slow nitrate-dependent growth of a napG mutant can be sustained by electron transfer from NrfH, the electron donor to the nitrite reductase NrfA. A napL mutant possessed approximately 50% lower NapA activity than the wild type but showed normal growth with nitrate as the electron acceptor. NrfA was constitutive and was shown to play a role in protection against nitrosative stress in addition to the previously identified NO-inducible single domain globin, Cgb. However, nitrite also induced cgb expression in an NssR-dependent manner, suggesting that growth of C. jejuni with nitrite causes nitrosative stress. This was confirmed by lack of growth of cgb and nssR mutants, and slow growth of the nrfA mutant, in media containing nitrite. Thus, NrfA and Cgb together provide C. jejuni with constitutive and inducible components of a robust defence against nitrosative stress.
    Molecular Microbiology 02/2007; 63(2):575-90. DOI:10.1111/j.1365-2958.2006.05532.x · 5.03 Impact Factor
Show more