Publications by authors named "Jeannette Winter"

Hypochlorite is a reactive oxygen species that is worldwide as an antibacterial disinfectant. Hypochlorite exposure is known to cause oxidative damage to DNA and proteins. As a response to these effects, the metabolite profiles of organisms treated with sub-lethal doses of hypochlorite are assumed to be severely modified; however, the nature of these changes is hardly understood.

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Exposure of cells to stress impairs cellular functions and may cause killing or adaptation. Adaptation can be facilitated by stress-induced mutagenesis or epigenetic changes, i.e.

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Sulfur-containing amino acids such as cysteine and methionine are particularly vulnerable to oxidation. Oxidation of cysteine and methionine in their free amino acid form renders them unavailable for metabolic processes while their oxidation in the protein-bound state is a common post-translational modification in all organisms and usually alters the function of the protein. In the majority of cases, oxidation causes inactivation of proteins.

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Hypochlorous acid (HOCl) is an important component of the immune system and is produced by neutrophils to kill invading microorganisms. The transcription factor HypT is specifically activated by HOCl by methionine oxidation and protects Escherichia coli cells from the detrimental effects of HOCl. HypT forms dodecameric ring-like oligomers.

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Reactive oxygen species are important components of the immune response. Hypochlorite (HOCl) is produced by neutrophils to kill invading microorganisms. The bactericidal activity of HOCl is due to proteome-wide unfolding and oxidation of proteins at cysteine and methionine residues.

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Oxidant-mediated antibacterial response systems are broadly used to control bacterial proliferation. Hypochlorite (HOCl) is an important component of the innate immune system produced in neutrophils and specific epithelia. Its antimicrobial activity is due to damaging cellular macromolecules.

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Hypochlorite is a powerful oxidant produced by neutrophils to kill invading microorganisms. Despite this important physiological role of HOCl in fighting bacterial infections, no hypochlorite-specific stress response has been identified yet. Here, we identified a hypochlorite-responsive transcription factor, YjiE, which is conserved in proteobacteria and eukaryotes.

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Protein disulfide isomerase (PDI) supports proinsulin folding as chaperone and isomerase. Here, we focus on how the two PDI functions influence individual steps in the complex folding process of proinsulin. We generated a PDI mutant (PDI-aba'c) where the b' domain was partially deleted, thus abolishing peptide binding but maintaining a PDI-like redox potential.

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Evolution depends on the acquisition of genomic mutations that increase cellular fitness. Here, we evolved Escherichia coli MG1655 cells to grow at extreme temperatures. We obtained a maximum growth temperature of 48.

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Hypochlorous acid (HOCl), the active ingredient of household bleach, functions as a powerful antimicrobial that is used not only in numerous industrial applications but also in mammalian host defence. Here we show that multicopy expression of cpdA, encoding the cAMP phosphodiesterase, leads to a dramatically increased resistance of Escherichia coli to HOCl stress as well as to the unrelated hydrogen peroxide (H(2)O(2)) stress. This general oxidative stress resistance is apparently caused by the CpdA-mediated decrease in cellular cAMP levels, which leads to the partial inactivation of the global transcriptional regulator cAMP receptor protein (CRP).

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The redox-regulated chaperone Hsp33 is specifically activated upon exposure of cells to peroxide stress at elevated temperatures. Here we show that Hsp33 harbors two interdependent stress-sensing regions located in the C-terminal redox-switch domain of Hsp33: a zinc center sensing peroxide stress conditions and an adjacent linker region responding to unfolding conditions. Neither of these sensors works sufficiently in the absence of the other, making the simultaneous presence of both stress conditions a necessary requirement for Hsp33's full activation.

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Molecular chaperones are an essential part of the universal heat shock response that allows organisms to survive stress conditions that cause intracellular protein unfolding. During the past few years, two new mechanisms have been found to control the activity of several chaperones under stress conditions-the regulation of chaperone activity by the redox state and by the temperature of the environment. Hsp33, for example, is redox-regulated.

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DnaK/DnaJ/GrpE constitutes the primary chaperone machinery in E. coli that functions to protect proteins against heat-induced protein aggregation. Surprisingly, upon exposure of cells to reactive oxygen species at elevated temperature, proteins are no longer protected by the DnaK system.

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The production of human proinsulin in Escherichia coli usually leads to the formation of inclusion bodies. As a consequence, the recombinant protein must be isolated, refolded under suitable redox conditions, and enzymatically converted to the biologically active insulin. In this study we describe a detailed in vitro renaturation protocol for human proinsulin that includes native structure formation and the enzymatic conversion to mature insulin.

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Recombinant production of native proinsulin in the periplasm of Escherichia coli is limited by formation of the correct disulfide bonds and inclusion body formation. These limitations can be overcome during in vitro folding of proinsulin by using a redox system and also protein disulfide isomerase. Here, we added a redox active substance, Vectrase-P, to the cultivation medium of E.

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Protein-disulfide isomerase (PDI) catalyzes the formation, rearrangement, and breakage of disulfide bonds and is capable of binding peptides and unfolded proteins in a chaperone-like manner. In this study we examined which of these functions are required to facilitate efficient refolding of denatured and reduced proinsulin. In our model system, PDI and also a PDI mutant having only one active site increased the rate of oxidative folding when present in catalytic amounts.

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