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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The AhpC subunit of the Bacillus subtilis alkyl hydroperoxide reductase was identified as a general stress protein induced in response to heat or salt stress or after entry of the organism into the stationary phase. The ahp operon, encoding the two subunits AhpC and AhpF, was cloned and localized between the gntRKPZ operon and the bglA locus. Two-dimensional gel analyses revealed an especially strong induction of AhpC and AhpF in cells subjected to oxidative stress. Transcriptional studies showed a 3- to 4-fold induction of ahp mRNA after heat or salt stress or starvation for glucose and a 20-fold induction by oxidative stress, thus confirming the protein induction data for AhpC and AhpF. Stress induction occurred at a sigmaA-dependent promoter that overlaps with operator sites similar to the per box. Compared with the wild type, the ahpC mutant was resistant to hydrogen peroxide because of the derepression of the peroxide regulon (N. Bsat, L. Chen, and J. D. Helmann, J. Bacteriol. 178:6579-6586, 1996) but more sensitive to cumene hydroperoxide (CHP) during exponential growth. In contrast, stationary-phase wild-type and ahpC mutant cells displayed complete resistance to treatment with 1 mM CHP. Moreover, a sigmaB mutant was found to be extremely sensitive to CHP during vegetative growth and in stationary phase, which indicates that sigmaB-dependent general stress proteins are involved in the protection of cells against oxidative stress.
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PMID:General and oxidative stress responses in Bacillus subtilis: cloning, expression, and mutation of the alkyl hydroperoxide reductase operon. 893 14

A computer-aided analysis of high resolution two-dimensional polyacrylamide gels was used to investigate the changes in the protein synthesis profile in B. subtilis wild-type strains and sigB mutants in response to heat shock, salt and ethanol stress, and glucose of phosphate starvation. The data provided evidence that the induction of a least 42 general stress proteins absolutely required the alternative sigma factor sigmaB. However, at least seven stress proteins, among them ClpC, ClpP, Sod, AhpC and AhpF, remained stress-inducible in a sigB mutant. Such a detailed analysis also premitted the description of subgroups of general stress proteins which are subject to additional regulatory circuits, indicating a very thorough fine-tuning of this complex response. The relative synthesis rate of the general stress proteins constituted up to 40% of the total protein synthesis of stressed cells and thereby emphasizes the importance of the stress regulon. Besides the induction of these general or rather unspecific stress proteins, the induction of stress-specific proteins is shown and discussed.
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PMID:Specific and general stress proteins in Bacillus subtilis--a two-deimensional protein electrophoresis study. 929 90

Three glutathione peroxidase homologs (YKL026C, YBR244W, and YIR037W/HYR1) were found in the Saccharomyces Genome Database. We named them GPX1, GPX2, and GPX3, respectively, and we investigated the function of each gene product. The gpx3Delta mutant was hypersensitive to peroxides, whereas null mutants of the GPX1 and GPX2 did not show any obvious phenotypes. Glutathione peroxidase activity decreased approximately 57 and 93% in the gpx3Delta and gpx1Delta/gpx2Delta/gpx3Delta mutants, respectively, compared with that of wild type. Expression of the GPX3 gene was not induced by any stresses tested, whereas that of the GPX1 gene was induced by glucose starvation. The GPX2 gene expression was induced by oxidative stress, which was dependent upon the Yap1p. The TSA1 (thiol-specific antioxidant) gene encodes thioredoxin peroxidase that can reduce peroxides by using thioredoxin as a reducing power. Disruption of the TSA1 gene enhanced the basal expression level of the Yap1p target genes such as GSH1, GLR1, and GPX2 and that resulted in increases of total glutathione level and activities of glutathione reductase and glutathione peroxidase. However, expression of the TSA1 gene did not increase in the gpx1Delta/gpx2Delta/gpx3Delta mutant. Therefore, de novo synthesis and recycling of glutathione were increased in the tsa1Delta mutant to maintain the catalytic cycle of glutathione peroxidase reaction efficiently as a backup system for thioredoxin peroxidase.
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PMID:Genetic analysis of glutathione peroxidase in oxidative stress response of Saccharomyces cerevisiae. 1048 Sep 13

Peroxisomes are ubiquitous eukaryotic organelles. The proteins required for peroxisome biogenesis are called peroxins, and mutations in the peroxin genes cause the devastating human developmental syndromes called the peroxisome biogenesis disorders. Our interest is in elaborating the roles that peroxisomes play in Caenorhabditis elegans development, and in establishing an invertebrate model system for the human peroxisome biogenesis disorders. The genome of C. elegans encodes homologs of 11 of the 13 human peroxins. We disrupted five nematode peroxins using RNA interference (RNAi) and found that RNAi knockdown of each one causes an early larval arrest at the L1 stage. Using a green fluorescent protein reporter targeted to the peroxisome, we establish that peroxisomal import is impaired in prx-5(RNAi) nematodes. prx-5(RNAi) animals are blocked very early in the L1 stage and do not initiate normal postembryonic cell divisions, similar to starvation-arrested larvae. Cell and axonal migrations that normally occur during the L1 stage also appear blocked. We conclude that peroxisome function is required for C. elegans postembryonic development and that disruption of peroxisome assembly by prx-5(RNAi) prevents scheduled postembryonic cell divisions. Defects in the cellular localization of peroxisomal proteins and in development are shared features of human and nematode peroxisome biogenesis disorders. In setting up a C. elegans model of peroxisomal biogenesis disorders, we suggest that genetic screens for suppression of the Prx developmental block will facilitate identification of novel intervention strategies and may provide new insights into human disease pathogenesis.
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PMID:Modeling human peroxisome biogenesis disorders in the nematode Caenorhabditis elegans. 1266 60

Responses of photosynthetic organisms to sulfur starvation include (i) increasing the capacity of the cell for transporting and/or assimilating exogenous sulfate, (ii) restructuring cellular features to conserve sulfur resources, and (iii) modulating metabolic processes and rates of cell growth and division. We used microarray analyses to obtain a genome-level view of changes in mRNA abundances in the green alga Chlamydomonas reinhardtii during sulfur starvation. The work confirms and extends upon previous findings showing that sulfur deprivation elicits changes in levels of transcripts for proteins that help scavenge sulfate and economize on the use of sulfur resources. Changes in levels of transcripts encoding members of the light-harvesting polypeptide family, such as LhcSR2, suggest restructuring of the photosynthetic apparatus during sulfur deprivation. There are also significant changes in levels of transcripts encoding enzymes involved in metabolic processes (e.g., carbon metabolism), intracellular proteolysis, and the amelioration of oxidative damage; a marked and sustained increase in mRNAs for a putative vanadium chloroperoxidase and a peroxiredoxin may help prolong survival of C. reinhardtii during sulfur deprivation. Furthermore, many of the sulfur stress-regulated transcripts (encoding polypeptides associated with sulfate uptake and assimilation, oxidative stress, and photosynthetic function) are not properly regulated in the sac1 mutant of C. reinhardtii, a strain that dies much more rapidly than parental cells during sulfur deprivation. Interestingly, sulfur stress elicits dramatic changes in levels of transcripts encoding putative chloroplast-localized chaperones in the sac1 mutant but not in the parental strain. These results suggest various strategies used by photosynthetic organisms during acclimation to nutrient-limited growth.
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PMID:Insights into the survival of Chlamydomonas reinhardtii during sulfur starvation based on microarray analysis of gene expression. 1547 Feb 61

Copper is an essential micronutrient for plants. Present at a high concentration in soil, copper is also regarded as a major toxicant to plant cells due to its potential inhibitory effects against many physiological and biochemical processes. The interference of germination-related proteins by heavy metals has not been well documented at the proteomic level. In the current study, physiological, biochemical and proteomic changes of germinating rice seeds were investigated under copper stress. Germination rate, shoot elongation, plant biomass, and water content were decreased, whereas accumulation of copper and TBARS content in seeds were increased significantly with increasing copper concentrations from 0.2mM to 1.5mM followed by germination. The SDS-PAGE showed the preliminary changes in the polypeptides patterns under copper stress. Protein profiles analyzed by two-dimensional electrophoresis (2-DE) revealed that 25 protein spots were differentially expressed in copper-treated samples. Among them, 18 protein spots were up-regulated and 7 protein spots were down-regulated. These differentially displayed proteins were identified by MALDI-TOF mass spectrometry. The up-regulation of some antioxidant and stress-related proteins such as glyoxalase I, peroxiredoxin, aldose reductase, and some regulatory proteins such as DnaK-type molecular chaperone, UlpI protease, and receptor-like kinase clearly indicated that excess copper generates oxidative stress that might be disruptive to other important metabolic processes. Moreover, down-regulation of key metabolic enzymes like alpha-amylase or enolase revealed that the inhibition of seed germinations after exposure to excess copper not only affects starvation in water uptake by seeds but also results in failure in the reserve mobilization processes. These results indicate a good correlation between the physiological and biochemical changes in germinating rice seeds exposed to excess copper.
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PMID:Excess copper induced physiological and proteomic changes in germinating rice seeds. 1718 80

A gene encoding a putative peroxiredoxin (Prx) of the fission yeast Schizosaccharomyces pombe was characterized and its regulation was studied. The full length of the prx gene was introduced into the shuttle vector pRS316 after PCR amplification, resulting in the recombinant plasmid pPrx10. The determined DNA sequence carries 1,327 bp encoding a putative Prx with a molecular mass of 19,510 Da. Prx activity was significantly increased in the S. pombe cells harboring pPrx10. The accelerated growth was observed in the S. pombe/pPrx10 cells, implying the involvement of the cloned gene in the yeast growth. To study transcriptional regulation of the prx gene, the prx-lacZ fusion gene was constructed using the yeast-E. coli shuttle vector YEp367R, and named pPrxup10. The synthesis of beta-galactosidase from the fusion gene was enhanced under carbon source-limited conditions and nitrogen starvation. Under the same growth conditions, the prx mRNA levels of the wild-type yeast cells were increased. The prx mRNA level was markedly decreased in the Pap1-negative mutant, compared with that in the wild-type yeast, suggesting that the basal expression of the prx gene is mediated by a transcription factor, Pap1. The reactive oxygen species (ROS) level was diminished in the S. pombe/pPrx10 cells than in the control cells. The extra copies of the prx gene were able to resist elevation of ROS level under limited carbon source condition and menadione treatment. In brief, the S. pombe Prx is linked with the yeast growth and up-regulated by metabolic oxidative stress on a transcriptional level. The Prx protein is partly responsible for maintaining low ROS level under normal and stressful growth conditions in the fission yeast.
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PMID:Molecular cloning, characterization and regulation of a peroxiredoxin gene from Schizosaccharomyces pombe. 1753 Apr 41

Phospholipid-hydroperoxide glutathione peroxidase (PHGPx or GPx4; EC 1.11.1.12) is an antioxidant enzyme that reduces lipid hydroperoxides in biomembranes. Here, we cloned and characterized cys-PHGPx from the bumblebee Bombus ignitus (Bi-PHGPx). The Bi-PHGPx gene consists of 4 exons, encoding 168 amino acid residues with a canonical cys-codon at residue 45 and active site residues Gln(82) and Trp(134). Recombinant Bi-PHGPx, expressed as a 19 kDa protein in baculovirus-infected insect cells, exhibited enzymatic activity against PLPC-OOH and H(2)O(2) using glutathione as an electron donor. Tissue distribution analyses showed the presence of Bi-PHGPx in all tissues examined. Bi-PHGPx transcripts were upregulated by stresses, such as wounding, H(2)O(2) exposure, external temperature shock, and starvation. Under H(2)O(2) overload, the RNA interference (RNAi)-induced thioredoxin peroxidase (BiTPx1)-knock-down B. ignitus worker bees showed upregulated expression of Bi-PHGPx in the fat body. These results indicate that Bi-PHGPx is a stress-inducible antioxidant enzyme that acts on phospholipid hydroperoxide and H(2)O(2).
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PMID:Molecular characterization of a phospholipid-hydroperoxide glutathione peroxidase from the bumblebee Bombus ignitus. 1980 99

The growth pattern and protein expression profiles of sheep (S) and cattle (C) strains of Mycobacterium avium subsp. paratuberculosis (MAP) under oxidative and nitrosative stress were characterised. Oxidative stress was induced using 0.05% (v/v) H(2)O(2) in BACTEC medium, and was lethal for an inoculum of 10(4) cells. However, an inoculum of 10(7) cells survived and proteomic changes were observed at 7 days. Nitrosative stress was induced using 1mM NaNO(2); it slowed the growth of an inoculum of 10(4) cells, but both strains recovered quickly when resuscitated in fresh media. Silver staining showed higher sensitivity for detection of 2D spots compared to SYPRO Ruby staining. A total of 18 proteins were regulated under oxidative and/or nitrosative stress. The expression of four antioxidant enzymes (AhpC, AhpD, OxcA and SodA) and four proteins involved in fatty acid metabolism (DesA2, FadA6_3, FabG and FadE19) was altered, together with a range of other proteins. Only one protein, AhpC was differentially regulated in both strains of MAP. Seven proteins (DesA2, AhpC, AhpD, Ppa, FabG, and hypothetical proteins MAP2411 and MAP 1885c) were identified in previous in vitro studies with temperature, hypoxia and/or nutrient starvation stressors and may be general stress response proteins of MAP. Prior studies have identified immune responses directed against AhpC and Ppa in animals with Johne's disease, expression of sodA and ppa within macrophages, and reduced virulence of impA mutants in mice, highlighting the relevance of proteomic studies using these in vitro stress models for pathogenesis studies.
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PMID:Partial proteome of Mycobacterium avium subsp. paratuberculosis under oxidative and nitrosative stress. 2041 29

Protein S-thiolation is a post-translational thiol-modification that controls redox-sensing transcription factors and protects active site cysteine residues against irreversible oxidation. In Bacillus subtilis the MarR-type repressor OhrR was shown to sense organic hydroperoxides via formation of mixed disulfides with the redox buffer bacillithiol (Cys-GlcN-Malate, BSH), termed as S-bacillithiolation. Here we have studied changes in the transcriptome and redox proteome caused by the strong oxidant hypochloric acid in B. subtilis. The expression profile of NaOCl stress is indicative of disulfide stress as shown by the induction of the thiol- and oxidative stress-specific Spx, CtsR, and PerR regulons. Thiol redox proteomics identified only few cytoplasmic proteins with reversible thiol-oxidations in response to NaOCl stress that include GapA and MetE. Shotgun-liquid chromatography-tandem MS analyses revealed that GapA, Spx, and PerR are oxidized to intramolecular disulfides by NaOCl stress. Furthermore, we identified six S-bacillithiolated proteins in NaOCl-treated cells, including the OhrR repressor, two methionine synthases MetE and YxjG, the inorganic pyrophosphatase PpaC, the 3-D-phosphoglycerate dehydrogenase SerA, and the putative bacilliredoxin YphP. S-bacillithiolation of the OhrR repressor leads to up-regulation of the OhrA peroxiredoxin that confers together with BSH specific protection against NaOCl. S-bacillithiolation of MetE, YxjG, PpaC and SerA causes hypochlorite-induced methionine starvation as supported by the induction of the S-box regulon. The mechanism of S-glutathionylation of MetE has been described in Escherichia coli also leading to enzyme inactivation and methionine auxotrophy. In summary, our studies discover an important role of the bacillithiol redox buffer in protection against hypochloric acid by S-bacillithiolation of the redox-sensing regulator OhrR and of four enzymes of the methionine biosynthesis pathway.
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PMID:S-bacillithiolation protects against hypochlorite stress in Bacillus subtilis as revealed by transcriptomics and redox proteomics. 2174 87


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