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.
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.
Elvers
Karen T
KT
School of Biomedical and Molecular Sciences, University of Surrey, Guildford GU2 7XH, UK.
Turner
Sue M
SM
Wainwright
Laura M
LM
Marsden
Gemma
G
Hinds
Jason
J
Cole
Jeffrey A
JA
Poole
Robert K
RK
Penn
Charles W
CW
Park
Simon F
SF
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D016123:Campylobacter jejuni / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002373:Cyclic AMP Receptor Protein; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D018869:Heat-Shock Response; D006454:Hemoglobins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007506:Iron-Sulfur Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D018384:Oxidative Stress; D011401:Promoter Regions, Genetic; D026361:Reactive Nitrogen Species / Q000378:metabolism; D011956:Receptors, Cell Surface; D018085:Regulon / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors; D014158:Transcription, Genetic; D054793:Truncated Hemoglobins
D001426:Bacterial Proteins; C489659:Cgb protein, Campylobacter jejuni; D002373:Cyclic AMP Receptor Protein; D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; D006454:Hemoglobins; D007506:Iron-Sulfur Proteins; D026361:Reactive Nitrogen Species; D011956:Receptors, Cell Surface; D014157:Transcription Factors; D054793:Truncated Hemoglobins; C481662:crp protein, E coli