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

On amino acid starvation, Escherichia coli cells exhibit an adaptive facility termed the stringent response. This is characterized by the production of high levels of a regulatory nucleotide, ppGpp, and concomitant curtailment in rRNA synthesis. Various studies reported earlier indicated that RNA polymerase is the site of action of ppGpp although a direct demonstration of the interaction of ppGpp with E. coli RNA polymerase is still lacking. Here we report the labelling of ppGpp with a fluorescent probe, 1-aminonapthalene-5-sulphonate (AmNS), at the terminal phosphates. AmNS-ppGpp responded much like a ppGpp molecule in an in vitro total transcription assay at selective promoters. Fluorescence titration of the tryptophan emission of RNA polymerase by AmNS-ppGpp indicated a unique binding site in the absence of template DNA. Competition experiments showed that unlabelled ppGpp binds to the enzyme at the same site. Sigma factor seems to have no effect on this binding. The titration profile is also characterized by a single slope in the Scatchard analysis. The presence of GTP or GDP does not influence the binding of AmNS-ppGpp with RNA polymerase. Forster's distance measurement was carried out which placed AmNS-ppGpp 27 A away from the rifampicin-binding domain of RNA polymerase.
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PMID:Evidence for a ppGpp-binding site on Escherichia coli RNA polymerase: proximity relationship with the rifampicin-binding domain. 774 47

A full-length cDNA clone for rat asparagine synthetase (AS) was isolated from a cDNA library enriched for amino acid-regulated sequences. The AS cDNA was used to investigate the amino acid-dependent repression of AS mRNA content in rat Fao hepatoma cells. In response to complete amino acid starvation, there was an approximately 10-fold increase in the level of AS mRNA. Three species of mRNA, of approx. sizes 2.0, 2.5 and 4.0 kb, were detected and each was simultaneously regulated to the same degree. The expression of AS mRNA increased by 6 h after removal of amino acids, reached a plateau after 9 h, and was blocked by either actinomycin D or cycloheximide. Partial repression of the AS mRNA content was maintained by the presence of a single amino acid in the culture medium, but the degree of effectiveness for each one varied widely. Glutamine showed the greatest ability to repress the AS mRNA content, even at an extracellular concentration 10 times below its plasma level. Other effective repressors included the amino acids asparagine, histidine and leucine, as well as ammonia. Depletion of selected single amino acids from an otherwise complete culture medium also caused up-regulation. In particular, removal of histidine, threonine or tryptophan from the medium, or the addition of histidinol to inhibit histidinyl-tRNA synthetase, resulted in a significant increase in AS mRNA content. The data indicate that nutrient regulation of AS mRNA occurs by a general control mechanism that is responsive to a spectrum of amino acids.
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PMID:Cloning of rat asparagine synthetase and specificity of the amino acid-dependent control of its mRNA content. 781 76

Saccharomyces cerevisiae mutant E124 was selected in a visual screen based on elongated cell shape. Genetic analysis showed that E124 contains two separate mutations, pps1-1 and elm4-1, each causing a distinct phenotype inherited as a single-gene trait. In rich medium, pps1-1 by itself causes increased doubling time but does not affect cell shape, whereas elm4-1 results in a moderate cell elongation phenotype but does not affect growth rate. Reconstructed elm4-1 pps1-1 double mutants display a synthetic phenotype in rich medium including extreme cell elongation and delayed cell separation, both characteristics of pseudohyphal differentiation. The elm4-1 mutation was shown to act as a dominant factor that potentiates pseudohyphal differentiation in response to general nitrogen starvation in a genetic background in which pseudohyphal growth normally does not occur. Thus, elm4-1 allows recognition of, or response to, a pseudohyphal differentiation signal that results from nitrogen limitation. PPS1 was isolated and shown to be a previously undescribed gene coding for a protein similar in amino acid sequence to phosphoribosylpyrophosphate synthase, a rate-limiting enzyme in the biosynthesis of nucleotides, histidine, and tryptophan. Thus, the pps1-1 mutation may generate a nitrogen limitation signal, which when coupled with elm4-1 results in pseudohyphal growth even in rich medium.
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PMID:The Saccharomyces cerevisiae mutation elm4-1 facilitates pseudohyphal differentiation and interacts with a deficiency in phosphoribosylpyrophosphate synthase activity to cause constitutive pseudohyphal growth. 800 70

A tryptophan-auxotrophic mutant of the archaeon Methanobacterium thermoautotrophicum Marburg was grown with growth-promoting and growth-limiting concentrations of tryptophan. The specific activities of anthranilate synthase (TrpEG) and tryptophan synthase (TrpB) increased 30- to 40-fold in tryptophan-starved cells. Levels of trpE-specific and trpD-specific mRNAs (transcripts of the first and the last genes, respectively, of the M. thermoautotrophicum Marburg trp gene cluster) increased about 10-fold upon starvation for tryptophan. Thus, the expression of the trp genes appears to be regulated primarily at the level of transcription. These data support transcription of trp genes as an operon and support a regulatory model involving a repressor. Anthranilate synthase was feedback inhibited by L-tryptophan, with a Ki of 3.0 microM. In a leucine-auxotrophic mutant starved for L-leucine, the level of alpha-isopropylmalate synthase (LeuA) was 10-fold higher than in cells grown with L-leucine. In addition to the finding of specific regulation of gene expression by the end products of their respective pathways, it was found that the levels of anthranilate synthase and alpha-isopropylmalate synthase were reduced upon growth in the presence of amino acids of other families, such as L-alanine, L-proline, or L-arginine. Conversely, starvation for tryptophan caused a slight elevation of alpha-isopropylmalate synthase and starvation for leucine caused a significant increase of anthranilate synthase and tryptophan synthase specific activities. The latter effect was also observed at the level of trp-specific mRNA and is reminiscent of general amino acid control.
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PMID:Regulation of tryptophan biosynthesis in Methanobacterium thermoautotrophicum Marburg. 804 89

In the thermophilic archaeon Methanobacterium thermoautotrophicum Marburg, the structural gene for isoleucyl-tRNA synthetase (ileS) is flanked upstream by orf401 and downstream by purL. orf401 encodes a 43.5-kDa protein with an unknown function. Northern (RNA) hybridization and S1 nuclease protection experiments showed that the orf401, ileS, and purL genes are cotranscribed from an archael consensus promoter in front of orf401. The corresponding transcript was about eightfold increased in cells that had been exposed to pseudomonic acid A, a specific inhibitor of isoleucyl-tRNA synthetase. Growth inhibition by puromycin, tryptophan starvation, or starvation for hydrogen did not affect the level of this transcript. The level of a trpE transcript, however, was drastically elevated upon tryptophan starvation, while inhibition by pseudomonic acid A had no effect on the level of this transcript. Expression of ileS thus appears to be controlled by a regulatory mechanism which specifically responds to the availability of isoleucyl-tRNA. Extensive decay of the orf401-ileS-purL message was observed. Degradation occurred, presumably by endonucleolytic cleavage, within the orf401 region.
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PMID:Transcription of the ileS operon in the archaeon Methanobacterium thermoautotrophicum Marburg. 837 40

Total blood and plasma free amino acids and plasma urea levels were studied in fed and 24 h fasted Zucker rats. In fed animals there were no differences between obese and lean rats in the overall essential and non essential blood free amino acids. However, starvation reduced blood amino acid levels in the obese animals compared to the lean group, mainly due to changes in the plasma compartment. The reduction of available amino acids from plasma in the obese rats during starvation affected most of the amino acids, including the branched chain amino acids, which showed higher levels in the fed situation than in lean rats. Of particular interest is the opposite response to starvation in lean and obese Zucker rats concerning the plasma ratio of tryptophan (Trp) to the large neutral amino acids (LNAA) which could be implicated in the alteration of food intake and energy expenditure characteristic of obesity.
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PMID:Opposite response to starvation of Trp/LNAA ratio in lean and obese Zucker rats. 848 65

Phosphoribosyl diphosphate-lacking (delta prs) mutant strains of Escherichia coli require NAD, guanosine, uridine, histidine, and tryptophan for growth. NAD is required by phosphoribosyl diphosphate-lacking mutants because of lack of one of the substrates for the quinolinate phosphoribosyltransferase reaction, an enzyme of the NAD de novo pathway. Several NAD-independent mutants of a host from which prs had been deleted were isolated; all of them were shown to have lesions in the pstSCAB-phoU operon, in which mutations lead to derepression of the Pho regulon. In addition NAD-independent growth was dependent on a functional quinolinate phosphoribosyltransferase. The prs suppressor mutations led to the synthesis of a new phosphoryl compound that may act as a precursor for a new NAD biosynthetic pathway. This compound may be synthesized by the product of an unknown phosphate starvation-inducible gene of the Pho regulon because the ability of pst or phoU mutations to suppress the NAD requirement requires PhoB, the transcriptional activator of the Pho regulon.
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PMID:Phosphoribosyl diphosphate synthetase-independent NAD de novo synthesis in Escherichia coli: a new phenotype of phosphate regulon mutants. 855 May 5

An investigation of the effects of chronic administration of ethanol by the liquid diet procedure and its subsequent withdrawal on tryptophan (Trp) metabolism and disposition was performed in rats. Treatment with the control liquid diet caused an enhancement of liver Trp pyrrolase activity and mRNA abundance. These effects are not due to the starvation associated with this feeding procedure, because they occur in rats maintained on the liquid diet ad libitum. Chronic ethanol administration in the liquid diet did not further influence the above increased expression of Trp pyrrolase mRNA but caused inhibition of pyrrolase activity in competition with the effects of the diet. The control liquid diet decreased liver Trp concentration, but exerted no significant effects on other aspects of Trp disposition. The most striking and robust finding was a highly significant elevation in both Trp pyrrolase activity and mRNA expression at 7 h following discontinuation of ethanol availability, at which time there were demonstrable behavioural signs of ethanol withdrawal. The increase in Trp pyrrolase mRNA during alcohol withdrawal may be caused by corticosterone, whose circulating concentration was also increased. The changes in Trp pyrrolase activity during ethanol withdrawal were associated with significant alterations in Trp disposition including decreased brain Trp concentration and 5-hydroxytryptamine synthesis and turnover. These alterations may play a pivotal role in the behavioural manifestations of ethanol withdrawal including the hyperexcitement underlying audiogenic seizures. We suggest that rat Trp pyrrolase gene regulation may be an important biological determinant of the ethanol withdrawal syndrome and requires further study, and that the use of the liquid diet procedure in Trp metabolic studies requires inclusion of adequate controls and special attention to the effects of the liquid diet itself.
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PMID:Effects of chronic administration and subsequent withdrawal of ethanol-containing liquid diet on rat liver tryptophan pyrrolase and tryptophan metabolism. 873 17

Rats fed on a restricted feeding (RF) schedule of 4 h day-1 to produce a 15-20% reduction in body weight were killed before (starved) and after (fed) the presentation of food on the sixth day to compare 5-hydroxytryptamine (5-HT; serotonin) metabolism and synthesis rate in the hypothalamus with freely feeding (FF) controls. The RF rats showed lower 5-HT concentration and synthesis rate than FF controls. Restricted feeding did not decrease tryptophan concentration in the hypothalamus. However, RF-fed rats had lower tryptophan concentration than RF starved rats. 5-HIAA concentration was comparable in RF fed rats and FF controls but higher in RF starved rats. Possible implications of the findings in the pathogenesis of the food deprivation/starvation-related disease anorexia nervosa are discussed.
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PMID:Food restriction decreases serotonin and its synthesis rate in the hypothalamus. 881 22

Indoleamine 2'3 dioxygenase (INDO), the rate-limiting enzyme in the catabolism of the essential amino acid L-tryptophan, is induced in many cell lines following interferon gamma (IFN-gamma) treatment. The induction of this enzyme has been associated with the antiparasitic and cytotoxic activities of human IFN-gamma. DNA analysis coupled to morphologic studies indicated that ME180 cells underwent apoptosis within 48 h of treatment with IFN-gamma. We hypothesized that apoptosis results from L-tryptophan starvation following INDO induction. This was confirmed by the prevention of apoptosis on adding back tryptophan to IFN-gamma-treated cells and the induction of apoptosis by removing tryptophan from the medium in the absence of IFN-gamma.
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PMID:Treatment of ME180 cells with interferon-gamma causes apoptosis as a result of tryptophan starvation. 888 61


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