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

Escherichia coli transports inorganic phosphate (Pi) by the low-affinity transport system, Pit. When the level of the external Pi is lower than 20 microM, another transport system, Pst, is induced with a Kt of 0.25 microM. An outer-membrane porin, PhoE, with a Km of about 1 microM is also induced. The outer membrane allows the intake of organic phosphates which are degraded to Pi by phosphatases in the periplasm. The Pi-binding protein will capture the free Pi produced in the periplasm and direct it to the transmembrane channel of the cytoplasmic membrane. The channel consists of two proteins, PstA and PstC, which have six and five transmembrane helices, respectively. On the cytoplasmic side of the membrane the channel is linked to the PstB protein, which carries a nucleotide (probably ATP)-binding site. PstB probably provides the energy required by the channel to free Pi. The Pst system has two functions in E. coli: (i) the transport of Pi, and (ii) the negative regulation of the phosphate regulon (a complex of 20 proteins mostly related to organic phosphate transport). It is remarkable that these two functions are not related, since the repressibility of the regulon depends on the integral structure of Pst (PiBP + PstA + PstC + PstB) and not on the Pi transported. Another gene of the pst operon, phoU, produces a protein involved in the negative regulation of the Pho regulon, but the mechanism of this function has not been explained. Thus the regulatory function of the Pst system remains obscure. Its basal level, present when Pi is abundant, is sufficient to repress the Pho regulon but the negative regulatory function is lost upon Pi starvation.
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PMID:Molecular aspects of phosphate transport in Escherichia coli. 170 Feb 57

The response of marine Vibrio sp. strain S14 (CCUG 15956) to long-term (48-h) multiple-nutrient starvation (i.e., starvation for glucose, amino acids, ammonium, and phosphate simultaneously) can be described as a three-phase process. The first phase, defined as the stringent control phase, encompasses an accumulation of guanosine 5'-diphosphate 3'-diphosphate (ppGpp) and decreases in RNA and protein synthesis during the first 40 min. In the second phase, there is a temporary increase in the rates of RNA and protein synthesis between 1 and 3 h paralleling a decrease in the ppGpp pool. The third phase includes gradual decline in macromolecular synthesis after 3 h. Using two-dimensional gel electrophoresis of pulse-labeled proteins, a total of 66 proteins were identified as starvation inducible (Sti), temporally expressed throughout the three phases of starvation. The inhibition of protein synthesis during the first phase of starvation partly disrupted the subsequent temporally ordered synthesis of starvation proteins and prevented the expression of some late starvation proteins. It was also found that the early temporal class of starvation proteins, which included the majority of the Sti proteins, was the most essential for long-term survival. Vibrio sp. strain S14 cultures prestarved (1 h) for glucose, amino acids, ammonium, or phosphate as well as cultures exposed (1 h) to CdCl2 exhibited enhanced survival during the subsequent multiple-nutrient starvation in the presence of chloramphenicol or rifampin, while heat or the addition of cyclic AMP or nalidixic acid prior to starvation had no effect. It was demonstrated that amino acid starvation and CdCl2 exposure, which induced the stringent response, were the most effective in conferring enhanced survival. A few Sti proteins were common to all starvation conditions. In addition, the total number of proteins induced by multiple-nutrient starvation significantly exceeded the sum of those induced by starvation for each of the individual nutrients.
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PMID:Responses to multiple-nutrient starvation in marine Vibrio sp. strain CCUG 15956. 170 28

The rpoS (katF) gene of Escherichia coli encodes a putative sigma factor (sigma S) required for the expression of a variety of stationary phase-induced genes, for the development of stationary-phase stress resistance, and for long-term starvation survival (R. Lange and R. Hengge-Aronis, Mol. Microbiol. 5:49-59, 1991). Here we show that the genes otsA, otsB, treA, and osmB, previously known to be osmotically regulated, are also induced during transition into stationary phase in a sigma S-dependent manner. otsA and otsB, which encode trehalose-6-phosphate synthase and trehalose-6-phosphate phosphatase, respectively, are involved in sigma S-dependent stationary-phase thermotolerance. Neither sigma S nor trehalose, however, is required for the development of adaptive thermotolerance in growing cells, which might be controlled by sigma E.
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PMID:Trehalose synthesis genes are controlled by the putative sigma factor encoded by rpoS and are involved in stationary-phase thermotolerance in Escherichia coli. 174 47

The gene products of the ugp operon of Escherichia coli are responsible for the uptake of sn-glycerol-3-phosphate and certain glycerophosphodiesters. The regulation of ugp is mainly phoBR-dependent. Significant expression, however, can be observed even in the presence of high concentrations of phosphate, a condition which normally completely represses pho expression. Pho-independent ugp expression was found to be derepressed during the late logarithmic growth phase due to carbon starvation. Among different carbon sources tested, glucose caused the most complete repression. Addition of cAMP prevented glucose repression, indicating that a cAMP-CRP control mechanism may be directly or indirectly involved in the carbon-starvation response. This conclusion is supported by the fact that pho-independent ugp expression correlated with the presence of the cya and crp gene products.
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PMID:Carbon-starvation induction of the ugp operon, encoding the binding protein-dependent sn-glycerol-3-phosphate transport system in Escherichia coli. 174 36

We have isolated a snf1/ccr1 mutant of Saccharomyces cerevisiae which loses viability upon starvation and fails to accumulate glycogen in response to abrupt depletion of phosphate or glucose. A snf1 null mutant is sensitive to heat stress and starvation and fails to accumulate glycogen during growth in rich medium. The phenotypes of the snf1 mutants are those commonly associated with an overactivation of the adenylate cyclase pathway. Mutations in adenylate cyclase or RAS2 which decrease the level of cAMP in the cell moderate the snf1 phenotype. In contrast, a mutation in RAS2 (RAS2val19) which increases the level of cAMP or a mutation in the regulatory subunit (BCY1) of cAMP-dependent protein kinase which results in unregulated cAMP-dependent protein kinase activity accentuates the snf1 phenotype. However, the action of SNF1 in the stress response appears at least partly independent of cAMP-dependent protein kinase because a snf1 phenotype is observed in a strain that lacks all three of the genes that encode the catalytic subunits of cAMP-dependent protein kinase. SNF1 therefore acts at least in part through a cAMP-independent pathway.
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PMID:Deletion of SNF1 affects the nutrient response of yeast and resembles mutations which activate the adenylate cyclase pathway. 175 15

The maximum activities of some key enzymes of metabolism were studied in lungs of fed and 48-h-starved rats. The maximum activity of hexokinase in the lung is similar to that of other tissues of the body, but lower than that of phosphorylase and 6-phosphofructokinase. High activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were found in lung tissue, suggesting the importance of the pentose phosphate pathway in the lung. The activities of hexokinase and 6-phosphofructokinase were decreased whereas that of phosphorylase increased in response to starvation. Of the enzymes of the tricarboxylic acid cycle whose activities were measured, that of oxoglutarate dehydrogenase was the lowest, yet its activity (approximately 4.2 nmol/min per mg protein at 37 degrees C) was considerably greater than the flux through the cycle (0.46 nmol/min per mg protein at 37 degrees C; calculated from oxygen consumption by incubated lung slices). The activities of both oxoglutarate dehydrogenase and citrate synthase were decreased by starvation. The activities of 3-oxoacid CoA-transferase and acetoacetyl-CoA thiolase were low in lung tissue compared to those of other tissues (eg kidney, brain) and that of 3-hydroxybutyrate dehydrogenase was very low. The activity of carnitine palmitoyl transferase is higher in the lung, suggesting that fatty acids (and possibly acetoacetate) could provide acetyl-CoA as substrate for the tricarboxylic acid cycle. Very low rates of utilization of 3-hydroxybutyrate were observed during incubation of lung slices, but that of oleate was 1.2 nmol/h per mg of protein.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Metabolism of glucose, glutamine, long-chain fatty acids and ketone bodies by lungs of the rat. 176

Alkaline phosphatase (APase) expression can be induced in Bacillus subtilis by phosphate starvation or by sporulation. We have recently shown that there are multiple APase structural genes contributing to the total alkaline phosphatase expression in B. subtilis. The expression of the alkaline phosphatase III gene (phoAIII) was analysed under both phosphate-starvation induction and sporulation induction conditions. phoAII is transcribed from two promoter regions, PV and PS. The PV promoter initiated transcription 37 bp before the translation initiation codon and was used to transcribe phoAIII during phosphate-starvation induction in vegetative cells. The PS promoter initiated transcription 119 bp before the translation initiation codon and was used during sporulation induction. Genes which have previously been shown to affect total vegatative APase, pho regulon genes phoP, phoR and phoS, affected expression of phoAIII during phosphate starvation. Genes known to affect expression of total sporulation APase, i.e. spoIIA, spoIIG and spoIIE, affected phoAIII expression during sporulation induction. Our data show that one member of the APase multigene family, phoAIII, contributes to the total APase expression both during phosphate-starvation induction and sporulation induction, and that the mechanism of regulation includes two promoters, each requiring different regulatory genes.
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PMID:Separate promoters direct expression of phoAIII, a member of the Bacillus subtilis alkaline phosphatase multigene family, during phosphate starvation and sporulation. 176 85

Phosphate uptake studies in different strains of the dimorphic pathogenic yeast Candida albicans were undertaken to show that this yeast actively transported phosphate with an apparent Km in the range of 90-170 microM. The uptake was pH dependent and derepressible under phosphate starvation. Vanadate-resistant (van) mutants of C. albicans showed a 20-70% reduction in the rate of phosphate uptake in high phosphate medium and was associated with an increased Km and reduced Vmax. The magnitude of derepression under phosphate starvation was different between van mutants. These results demonstrate that van mutants may have developed resistance by modifying the rate of entry of vanadate.
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PMID:Vanadate-resistant mutants of Candida albicans show alterations in phosphate uptake. 177 39

Subtractive differential hybridization was used to identify genes in Bacillus subtilis that are induced by nutrient limitation. Several transcription units were identified. They exhibited increased transcription when cells were deprived of certain nutrients, such as glucose, ammonium, or phosphate, or when cells were treated with decoyinine. The genes have been designated dci (for decoyinine-inducible) and gsi (for glucose-starvation-inducible). Using lacZ transcriptional fusions, the dependence of dci and gsi expression on gene products of the sensor and activator classes of bacterial two-component regulatory systems was examined. Transcription of dciA was impaired by a mutation in spoOA, while expression of gsiA was dependent on the early competence genes comP and comA. The implications of these findings are discussed, and a provisional scheme for information flow during the transition phase from growth to sporulation is proposed.
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PMID:Identification of Bacillus subtilis adaptive response genes by subtractive differential hybridization. 178 20

The cations Ca2+ and K+ and the anions Cl-, HCO3-, and PO4- were studied for their contribution to metacyclic trypomastigote formation of Trypanosoma cruzi in starvation media consisting of phosphate-buffered saline (PBS) + 10 mM proline + 10 mM sodium acetate as well as one of the following salts: 0.035% NaHCO3 (PBSNPA), 0.035% K2CO3 (PBSKPA) or 0.035% K2HPO4 (PBSPPA). Isolates CL and DM28c were activated to transform with 5% CO2 and the percent metacyclogenesis determined after incubation for 96 h in PBS starvation media. Maximal metacyclogenesis was found with CaCl2 and KCl. In the presence of K+, the percent transformation was highest with the phosphate salt, followed by the carbonate and the chloride salts. Cells incubated in PBSNPA and the cationic ionophores A23187 (5 x 10(-6) M), lasalocid (5 x 10(-6) M), and valinomycin (10(-8) M) do not survive; addition of 2 mM CaCl2 or 17 mM KCl to DM28c cells, reversed the lethal action of the ionophores permitting differentiation into metacyclic forms. The addition of CaCl2 to CL cells incubated in ionophores abrogated the lethal effect of the ionophores but transformation was significantly different than in control preparations. Adding KCl to ionophore incubated cells resulted in normal levels of transformation except in the case of valinomycin. DM28c and CL cells incubated in PBSKPA show significantly greater metacyclogenesis in the presence of 5 mM EGTA. These results indicate that exogenous concentrations of several cations and anions significantly influence T. cruzi metacyclogenesis and that the degree of response by the parasite to free ion levels may be strain dependent.
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PMID:Action of exogenous potassium and calcium ions on in vitro metacyclogenesis in Trypanosoma cruzi. 181 6


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