Regulation of Catalase-Peroxidase KatG Is OxyR Dependent and Fur Independent in Caulobacter crescentus

Abstract

Most organisms that grow in the presence of oxygen possess catalases and/or peroxidases, which are necessary for scavenging the H 2 O 2 produced by aerobic metabolism. In this work we investigate the pathways that regulate the Caulobacter crescentus katG gene, encoding the only enzyme with catalase-peroxidase function in this bacterium. The transcriptional start site of the katG gene was determined, showing a short 5 untranslated region. The katG regulatory region was mapped by serial deletions, and the results indicate that there is a single promoter, which is responsible for induction at stationary phase. An oxyR mutant strain was constructed; it showed decreased katG expression, and no KatG protein or catalase-peroxidase activity was detected in stationary-phase cell extracts, implying that OxyR is the main positive regulator of the C. crescentus katG gene. Purified OxyR protein bound to the katG regulatory region between nucleotides ؊42 and ؊91 from the transcription start site, as determined by a DNase I footprinting assay, and a canonical OxyR binding site was found in this region. Moreover, OxyR binding was shown to be redox dependent, given that only oxidized proteins bound adjacent to the ؊35 sequence of the promoter and the katG P1 promoter was activated by OxyR in an H 2 O 2 -dependent manner. On the other hand, this work showed that the iron-responsive regulator Fur does not regulate C. crescentus katG, since a fur mutant strain presented wild-type levels of katG transcription and catalase-peroxidase production and activity, and the purified Fur protein was not able to bind to the katG regulatory region.

Extracytoplasmic function (ECF) sigma factor σF is involved in Caulobacter crescentus response to heavy metal stress

“…In agreement, transcript levels of CC3255 and CC3252 were also not influenced by any of these stressors in cells lacking sigF . Concentrations of hydrogen peroxide and t-butyl hydroperoxide used in our analyses were previously found to be sufficient to increase expression of other genes in C. crescentus [15,18]. Taken together, these data suggest that chromium and cadmium are able to induce the σ F regulon in an oxidative stress independent manner.…”

The Caulobacter crescentus Homolog of DnaA (HdaA) Also Regulates the Proteolysis of the Replication Initiator Protein DnaA

“…6, C. crescentus cells start to remove DnaA protein well before they stop growing. C. crescentus clearly has a complex stationary-phase program(s) (48)(49)(50)(51)(52), and DnaA is not just a replication factor: DnaA is also a global regulator of many genes (36). In light of our results, we propose that HdaA is not only a RIDA component but also a key component of the programs that prepare cells for survival in the stationary phase.…”

Towards an Informative Mutant Phenotype for Every Bacterial Gene

“…As a specific example, ZMO1733 belongs to the LysR family of regulators and has cofitness with several genes that are important for resisting oxidative stresses, including an adjacent alkyl hydroperoxide reductase (ZMO1732), which suggests that ZMO1733 is involved in responding to oxidative stresses. Indeed, the ortholog of ZMO1733 in Caulobacter crescentus was recently shown to be the redox-sensitive regulator OxyR (39). Furthermore, three of these transcription factors contain response regulator domains, and all three of these have high cofitness with nearby histidine kinases, which presumably regulate the activity of these transcription factors.…”