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: 4.42). 09/2005; 57(3):735-50. DOI: 10.1111/j.1365-2958.2005.04723.x
Source: PubMed


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.

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Available from: Gemma L Marsden, Nov 05, 2014
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    • "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 . "
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