The yjeB ( nsrR ) Gene of Escherichia coli Encodes a Nitric Oxide-Sensitive Transcriptional Regulator

Abstract

Microarray studies of the Escherichia coli response to nitric oxide and nitrosative stress have suggested that additional transcriptional regulators of this response remain to be characterized. We identify here the product of the yjeB gene as a negative regulator of the transcription of the ytfE, hmpA and ygbA genes, all of which are known to be upregulated by nitrosative stress. Transcriptional fusions to the promoters of these genes were expressed constitutively in a yjeB mutant, indicating that all three are targets for repression by YjeB. An inverted repeat sequence that overlaps the ؊10 element of all three promoters is proposed to be a binding site for the YjeB protein. A similar inverted repeat sequence was identified in the tehA promoter, which is also known to be sensitive to nitrosative stress. The ytfE, hmpA, ygbA, and tehA promoters all caused derepression of a ytfE-lacZ transcriptional fusion when present in the cell in multiple copies, presumably by a repressor titration effect, suggesting the presence of functional YjeB binding sites in these promoters. However, YjeB regulation of tehA was weak, as judged by the activity of a tehA-lacZ fusion, perhaps because YjeB repression of tehA is masked by other regulatory mechanisms. Promoters regulated by YjeB could be derepressed by iron limitation, which is consistent with an iron requirement for YjeB activity. The YjeB protein is a member of the Rrf2 family of transcriptional repressors and shares three conserved cysteine residues with its closest relatives. We propose a regulatory model in which the YjeB repressor is directly sensitive to nitrosative stress. On the basis of similarity to the nitrite-responsive repressor NsrR from Nitrosomonas europaea, we propose that the yjeB gene of E. coli be renamed nsrR.

Role of flavohemoglobin in combating nitrosative stress in uropathogenic Escherichia coli – Implications for urinary tract infection

“…The regulation of hmp transcription is complex involving several regulators including Fnr [12] and MetR [13]. Recently, it was discovered that the regulator NsrR represses hmp transcription in the absence of NO or nitrite [14,15]. NsrR is proposed to contain a NO-labile [Fe-S] cluster responsible for the NO-sensing capacity [14].…”

“…Recently, it was discovered that the regulator NsrR represses hmp transcription in the absence of NO or nitrite [14,15]. NsrR is proposed to contain a NO-labile [Fe-S] cluster responsible for the NO-sensing capacity [14]. The importance of Hmp as a mechanism of protection from endogenous hostderived NO has so far been shown in human macrophages challenged with Salmonella enterica and non-pathogenic E. coli [16,17,18].…”

Determination of the Escherichia coli S-Nitrosoglutathione Response Network Using Integrated Biochemical and Systems Analysis

“…Additionally, NO can freely diffuse across membranes, whereas, GSNO susceptibility has been shown to be dependent on the Dpp dipeptide ABC transporter in Salmonella (12)(13)(14). As the first step for studying RNS challenge in E. coli, previous investigations often did not distinguish between RSNO and NO-mediated effects (15,16) and RSNOs were sometimes used as NO donors (17). Such studies set the foundation for further distinction between RSNO and NO.…”

“…coli possesses a NO-specific response network: the transcription factors (TFs) NorR and NsrR mediate increased expression of defense proteins NO reductase NorV and NO dioxygenase HmpA, respectively, in response to NO (17,19,20). Using a systems analysis (21), we have shown that, consistent with the known chemistry, NO primarily affects E. coli by reacting with metal groups, including those in the cytochrome oxidases, the Fe-S clusters of IscR, and branched chain amino acid (BCAA) synthesis protein dihydroxy acid dehydratase (IlvD).…”

Inefficient translation of nsrR constrains behaviour of the NsrR regulon in Escherichia coli

“…The cluster is likely to be [4Fe-4S], and reaction with NO is accompanied by a decrease in DNA binding affinity and de-repression of NsrR-regulated promoters (Bodenmiller & Spiro, 2006;Tucker et al, 2008;Yukl et al, 2008;Crack et al, 2015). The previously characterized NsrR regulon includes genes encoding the NO-scavenging flavohaemoglobin (hmp), the RIC (repair of iron centres) protein that participates in the repair of NO-damaged [Fe-S] clusters (ytfE), the respiratory nitrite reductase Nrf that is also an NO reductase (nrfABCDEFG), genes involved in motility ( fliA) and aromatic amine metabolism (tynA, feaB), and genes of unknown function, for example ygbA, yccM and yeaR-yoaG (Bodenmiller & Spiro, 2006;Filenko et al, 2007;Lin et al, 2007;Rankin et al, 2008;Partridge et al, 2009). The NsrR binding site is an 11-1-11 bp inverted repeat of the consensus motif AAGATGCYTTT (Bodenmiller & Spiro, 2006).…”