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PH dependence of the stress regulator DksA.

ABSTRACT: DksA controls transcription of genes associated with diverse stress responses, such as amino acid and carbon starvation, oxidative stress, and iron starvation. DksA binds within the secondary channel of RNA polymerase, extending its long coiled-coil domain towards the active site. The cellular expression of DksA remains constant due to a negative feedback autoregulation, raising the question of whether DksA activity is directly modulated during stress. Here, we show that Escherichia coli DksA is essential for survival in acidic conditions and that, while its cellular levels do not change significantly, DksA activity and binding to RNA polymerase are increased at lower pH, with a concomitant decrease in its stability. NMR data reveal pH-dependent structural changes centered at the interface of the N and C-terminal regions of DksA. Consistently, we show that a partial deletion of the N-terminal region and substitutions of a histidine 39 residue at the domain interface abolish pH sensitivity in vitro. Together, these data suggest that DksA responds to changes in pH by shifting between alternate conformations, in which competing interactions between the N- and C-terminal regions modify the protein activity.

SUBMITTER: Furman R

PROVIDER: S-EPMC4370453 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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pH dependence of the stress regulator DksA.

Furman Ran R Danhart Eric M EM NandyMazumdar Monali M Yuan Chunhua C Foster Mark P MP Artsimovitch Irina I

PloS one 20150323 3

DksA controls transcription of genes associated with diverse stress responses, such as amino acid and carbon starvation, oxidative stress, and iron starvation. DksA binds within the secondary channel of RNA polymerase, extending its long coiled-coil domain towards the active site. The cellular expression of DksA remains constant due to a negative feedback autoregulation, raising the question of whether DksA activity is directly modulated during stress. Here, we show that Escherichia coli DksA is ...[more]

PMID: 25799498

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Project description:Redox-based signaling is fundamental to the capacity of bacteria to sense, and respond to, nitrosative and oxidative stress encountered in natural and host environments. The conserved RNA polymerase regulatory protein DksA is a thiol-based sensor of reactive nitrogen and oxygen species. DksA-dependent transcriptional control promotes antinitrosative and antioxidative defenses that contribute to Salmonella pathogenesis. The specific adaptive changes mediated by DksA in response to reactive species, however, have not been elucidated. Herein, we characterize DksA-dependent changes in gene expression in Salmonella enterica experiencing nitrosative stress. Genome-wide expression analysis of wild-type and ?dksA Salmonella exposed to the nitric oxide ((•)NO) donor DETA NONOate demonstrated (•)NO- and DksA-dependent regulatory control of 427 target genes. Transcriptional changes centered primarily on genes encoding aspects of cellular metabolism. Several antioxidants and oxidoreductases important in redox buffering, (•)NO detoxification, and damage repair were also observed to be up-regulated in an (•)NO- and DksA-dependent manner. Compared to wild-type bacteria, (•)NO-treated ?dksA Salmonella exhibited a de-repression of genes encoding components of iron homeostasis and failed to activate sulfur assimilation and cysteine biosynthetic operons. As cysteine is integral to efficient antinitrosative and antioxidative defense and repair programs, we further examined the redox-responsive transcriptional control of cysteine biosynthesis by DksA. These investigations revealed that the activation of genes comprising cysteine biosynthesis also occurs in response to hydrogen peroxide, is dependent upon the redox-sensing zinc finger motif of DksA, and requires the transcriptional regulator CysB. Our observations demonstrate that DksA mediates global adaptation to nitrosative stress in Salmonella and provide unique insight into a novel regulatory mechanism by which cysteine biosynthesis is controlled in response to reactive oxygen and nitrogen species.

Dataset Information

PH dependence of the stress regulator DksA.

Publications

pH dependence of the stress regulator DksA.

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