Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pseudomonas fluorescens DR54 showed antagonistic properties against plant pathogenic Pythium ultimum and Rhizoctonia solani both in vitro and in planta. Antifungal activity was extractable from spent growth media, and fractionation by semi-preparative HPLC resulted in isolation of an active compound, which was identified as a new bacterial cyclic lipodepsipeptide, viscosinamide, using 1D and 2D 1H-, 13C-NMR and mass spectrometry. The new antibiotic has biosurfactant properties but differs from the known biosurfactant, viscosin, by containing glutamine rather than glutamate at the amino acid position 2 (AA2). No viscosin production was observed, however, when Ps. fluorescens DR54 was cultured in media enriched with glutamate. In vitro tests showed that purified viscosinamide also reduced fungal growth and aerial mycelium development of both P. ultimum and R. solani. Viscosinamide production by Ps. fluorescens DR54 was tightly coupled to cell proliferation in the batch cultures, as the viscosinamide produced per cell mass unit approached a constant value. In batch cultures with variable initial C, N or P nutrient levels, there were no indications of elevated viscosinamide production during starvation or maintenance of the cultures in stationary phase. Analysis of cellular fractions and spent growth media showed that a major fraction of the viscosinamide produced remained bound to the cell membrane of Ps. fluorescens DR54. The isolation, determination of structure and production characteristics of the new compound with both biosurfactant and antibiotic properties have promising perspectives for the application of Ps. fluorescens DR54 in biological control.
 ...
PMID:Viscosinamide, a new cyclic depsipeptide with surfactant and antifungal properties produced by Pseudomonas fluorescens DR54. 1043 90

The content of inorganic linear polyphosphate (polyP) and the polymeric degree (n) of these compounds were determined in the process of growth of the yeast Saccharomyces cerevisiae VKM Y-1173 in a medium, which contained varying Pi amount with the constant level of all the necessary components. For this purpose, a combination of chemical methods of polyP extraction and 31P-NMR spectroscopy studies of their chain length were used. After 7 h of phosphate starvation, the yeast was shown to use almost completely the phosphate reserve in the form of polyP localized in various cell compartments to support their vitality. The polyP drop was followed by a considerable shortening of the polymer chain length of acid-soluble (polyP1) and two alkali-soluble (polyP3 and polyP4) fractions. Under the same conditions, the content of a salt-soluble fraction (polyP2) decreased almost 20-fold followed by a simultaneous increase of the chain length nearly 2-fold. As a result, fraction chain length ranged up to n = 40-45. Replacement of the yeast cells after phosphate starvation to a complete phosphate- and glucose-containing medium resulted in super-accumulation ("overcompensation") of polyP within 2 h mainly in polyP3 and, to a lesser degree, in polyP1, polyP2, and polyP5 fractions. In polyP4 fraction localized as polyP3 at the cell surface, the polyP super-accumulation was not detected. The increase of polyP amount in the fractions mentioned turned out not to be accompanied by simultaneous elongation of their chain length and occurred at the lowest level that is characteristic of a polymer level for each fraction. Further cultivation of the yeast on the complete medium during 2 h had little or no effect on polyP content in the cells but led to elongation of polyP chain length especially in the polyP3 and polyP4 fractions. A phenomenon of considerable elongation of polyP chain length against the background of their fixed content revealed in the yeast growing on the complete medium suggests that these organisms possess a previously unknown discrete way of polyP biosynthesis, which results first in the formation of comparatively low-molecular-mass chains followed by that of high-molecular-mass polymers.
 ...
PMID:Dependence of inorganic polyphosphate chain length on the orthophosphate content in the culture medium of the yeast Saccharomyces cerevisiae. 1073 78

The effects of mannose (Man) and glucose (Glc) on central metabolism, proteolysis, and expression of the root starvation-induced protease (RSIP; F. James, R. Brouquisse, C. Suire, A. Pradet, P. Raymond [1996] Biochem J 320: 283-292) were investigated in maize (Zea mays L. cv DEA) root tips. Changes in metabolite concentrations (sugars, ester-phosphates, adenine nucleotides, and amino acids) were monitored using in vivo and in vitro (13)C- and (31)P-NMR spectroscopy, in parallel with the changes in respiration rates, protein contents, proteolytic activities, and RSIP amounts. The inhibition of proteolysis, the decrease in proteolytic activities, and the repression of RSIP expression triggered by Man, at concentrations usually used to study sugar signaling (2 and 10 mM), were found to be related to a drop of energy metabolism, primarily due to a Man-induced Pi sequestration. However, when supplied at low concentration (2 mM) and with the adequate phosphate concentration (30 mM), energy metabolism was restored and Man repressed proteolysis similarly to Glc, when provided at the same concentration. These results indicate that Man should be used with caution as a Glc analog to study signalization by sugars in plants because possible signaling effects may be hindered by Pi sequestration.
 ...
PMID:Regulation of protein degradation and protease expression by mannose in maize root tips. Pi sequestration by mannose may hinder the study of its signaling properties. 1124 27

The principle substrate for brain metabolism is glucose, which provides both energy and the carbon skeletons of glutamate and glutamine, via the TCA cycle. The existence of two distinct cerebral metabolic compartments, neurons and glia, involved in glutamate and glutamine synthesis, respectively, is a widely accepted concept. In previous work, the relative glucose flux via pyruvate dehydrogenase (PDH) and pyruvate carboxylase (PC) in adult rabbit brain, using 13C NMR isotopomer analysis of glutamate and glutamine, was quantified. In this work, manifestation of cerebral compartmentation in the near-term fetal rabbit was investigated, using the above approach. Following infusion of [U-13C]glucose into maternal circulation (1 mg/kg per min) for 60-70 min, fetal brains were excised and brain extracts were studied by 13C NMR. The labelling patterns of fetal cerebral metabolites differed from those observed in the young adult brain. The most significant differences were found for glutamine labelling patterns. We suggested that these differences are a result of increased utilization of non-labeled fuels, mainly beta-hydroxybutyrate (beta-HBA) in the glia, the site of glutamine synthesis. In addition, we have shown that acute exposure to elevated beta-HBA levels leads to increased uptake, but not utilization, into the fetal rabbit brain; no increase in uptake is observed in the adult brain. We have also demonstrated that during short-term starvation, although no changes are detected in plasma and cerebral glucose levels in the fetal and young adult brain, amino acid levels and energy metabolism are altered in the young adult brain.
 ...
PMID:Energy fuel utilization by fetal versus young rabbit brain: a 13C MRS isotopomer analysis of [U-(13)C]glucose metabolites. 1127 79

The influence of phosphite (H2PO3-) on the response of Saccharomyces cerevisiae to orthophosphate (HPO4(2-); Pi) starvation was assessed. Phosphate-repressible acid phosphatase (rAPase) derepression and cell development were abolished when phosphate-sufficient (+Pi) yeast were subcultured into phosphate-deficient (-Pi) media containing 0.1 mM phosphite. By contrast, treatment with 0.1 mM phosphite exerted no influence on rAPase activity or growth of +Pi cells. 31P NMR spectroscopy revealed that phosphite is assimilated and concentrated by yeast cultured with 0.1 mM phosphite, and that the levels of sugar phosphates, pyrophosphate, and particularly polyphosphate were significantly reduced in the phosphite-treated -Pi cells. Examination of phosphite's effects on two PHO regulon mutants that constitutively express rAPase indicated that (i) a potential target for phosphite's action in -Pi yeast is Pho84 (plasmalemma high-affinity Pi transporter and component of a putative phosphate sensor-complex), and that (ii) an additional mechanism exists to control rAPase expression that is independent of Pho85 (cyclin-dependent protein kinase). Marked accumulation of polyphosphate in the delta pho85 mutant suggested that Pho85 contributes to the control of polyphosphate metabolism. Results are consistent with the hypothesis that phosphite obstructs the signaling pathway by which S. cerevisiae perceives and responds to phosphate deprivation at the molecular level.
 ...
PMID:Phosphite disrupts the acclimation of Saccharomyces cerevisiae to phosphate starvation. 1176 57

The correlation between iron chlorosis resistance and induction of adaptive mechanisms in grapevine calli belonging to cultivars with different susceptibility to iron chlorosis has been investigated. Fe(III)-chelate reductase was clearly linked to the Fe-efficiency status of the genotype. When growing on iron deprived medium (-Fe) calli of the Fe-efficient genotype "Cabernet sauvignon" showed a remarkable increase in enzyme activity, up to five times higher, with respect to +Fe cultures. Moreover, 31P-NMR revealed that in -Fe medium the increase of vacuolar Pi content of the Fe-efficient cultures was more pronounced than that recorded for the Fe-inefficient Vitis riparia. Furthermore, Fe starvation also enhanced the production of phenolic compounds in calli of "Cabernet sauvignon" with respect to those of Vitis riparia. The role of H(+)-ATPase as a marker of Fe-efficiency in tissue culture remains ambiguous in the case of grapevines.
 ...
PMID:Adaptive responses to iron-deficiency in callus cultures of two cultivars of Vitis spp. 1296 62

The neuronal calcium sensor (NCS) proteins (e.g. recoverin, neurocalcins, and frequenin) are expressed at highest levels in excitable cells, and some of them regulate desensitization of G protein-coupled receptors. Here we present NMR analysis and genetic functional studies of an NCS homolog in fission yeast (Ncs1p). Ncs1p binds three Ca2+ ions at saturation with an apparent affinity of 2 microm and Hill coefficient of 1.9. Analysis of NMR and fluorescence spectra of Ncs1p revealed significant Ca2+-induced protein conformational changes indicative of a Ca2+-myristoyl switch. The amino-terminal myristoyl group is sequestered inside a hydrophobic cavity of the Ca2+-free protein and becomes solvent-exposed in the Ca2+-bound protein. Subcellular fractionation experiments showed that myristoylation and Ca2+ binding by Ncs1p are essential for its translocation from cytoplasm to membranes. The ncs1 deletion mutant (ncs1Delta) showed two distinct phenotypes: nutrition-insensitive sexual development and a growth defect at high levels of extracellular Ca2+ (0.1 m CaCl(2)). Analysis of Ncs1p mutants lacking myristoylation (Ncs1p(G2A)) or deficient in Ca2+ binding (Ncs1p(E84Q/E120Q/E168Q)) revealed that Ca2+ binding was essential for both phenotypes, while myristoylation was less critical. Exogenous cAMP, a key regulator for sexual development, suppressed conjugation and sporulation of ncs1Delta, suggesting involvement of Ncs1p in the adenylate cyclase pathway turned on by the glucose-sensing G protein-coupled receptor Git3p. Starvation-independent sexual development of ncs1Delta was also complemented by retinal recoverin, which controls Ca2+-regulated desensitization of rhodopsin. In contrast, the Ca2+-intolerance of ncs1Delta was not affected by cAMP or recoverin, suggesting that the two ncs1Delta phenotypes are mechanistically independent. We propose that Schizosaccharomyces pombe Ncs1p negatively regulates sporulation perhaps by controlling Ca2+-dependent desensitization of Git3p.
 ...
PMID:Fission yeast homolog of neuronal calcium sensor-1 (Ncs1p) regulates sporulation and confers calcium tolerance. 1472 91

Deoxynivalenol (DON) is a trichothecene secondary metabolite produced by Fusarium species infecting cereal crops. As a mycotoxin, DON causes losses in livestock production and poses a health risk to humans consuming contaminated cereal products. DON also acts as a virulence factor, facilitating the colonization of host plants by Fusarium spp. Enzymatic detoxification of mycotoxins in feed additives and genetically modified crops is a promising approach for the reduction of mycotoxin contamination of feeds and food. A prerequisite for the development of biotechnological strategies for DON detoxification is the availability of genes encoding suitable enzymatic activities. With the goal of isolating microbial cultures that can be used as a source of such activities, we screened 1285 microbial cultures from farmland soil, cereal grains, insects and other sources for DON transformation under aerobic conditions. One mixed culture transformed DON into two chromatographically separable products. The main product of the transformation was purified and its structure was elucidated by mass spectroscopy, (1)H-NMR, (13)C-NMR and proton-proton and carbon-proton correlated NMR spectroscopy. The structure of this product was determined to be 3-keto-4-deoxynivalenol. The DON-transforming mixed culture survived and retained its transforming activity during a starvation period of six months at 20 degrees C. Transformation of DON was suppressed by low concentrations of glucose and high concentrations of tryptone and yeast extract. Cell-free supernatants obtained either by filtration through a 0.22 microm membrane filter or by centrifugation did not exert DON-transforming activity. Trichothecenes 15-acetyl-DON, 3-acetyl-DON and fusarenon-X were also transformed.
 ...
PMID:Microbial detoxification of mycotoxin deoxynivalenol. 1506 74

Lactococcus lactis strain NZ9000(pNZpyk), which overproduces pyruvate kinase (PK), was constructed. The pNZpyk plasmid carries the P(nisA)-pyk transcriptional fusion, and the overexpression of its pyk gene was accomplished by using the nisin-inducible expression system of the NZ9000 strain. In vivo (13)C- and (31)P-NMR spectroscopy was used to evaluate the effect of this modification on the metabolism of glucose in non-growing cells. A detailed description of the kinetics of glucose, end products, glycolytic intermediates, NAD(+) and NADH was obtained. A 15-fold increase in the level of PK did not increase the overall glycolytic flux, which, on the contrary, was slightly reduced. Significant differences were observed in (i) the level of 3-phosphoglycerate (3-PGA) and phosphoenolpyruvate (PEP), metabolites associated with starvation; (ii) the rate of fructose 1,6-bisphosphate (FBP) depletion upon glucose exhaustion; and (iii) the NAD(+)/NADH ratio during glucose catabolism. In the mutant, the rate of FBP consumption after glucose depletion was notably accelerated under anaerobic conditions, whereas 3-PGA and PEP decreased to undetectable levels. Furthermore, the level of NAD(+) decreased steadily during the utilization of glucose, probably due to the unanticipated reduction in the lactate dehydrogenase activity in comparison with the control strain, NZ9000(pNZ8020). The results show that PK is an important bottleneck to carbon flux only when glucose becomes limiting; in the overproducer this constriction was no longer present, as evidenced by the faster FBP consumption and lack of accumulation of 3-PGA and PEP in anaerobic as well as aerobic conditions. Despite these clear changes, the PK-overproducing strain showed typical homolactic metabolism under anaerobic conditions, as did the strain harbouring the vector plasmid without the pyk insert. However, under an oxygen atmosphere, there was increased channelling of carbon to the production of acetate and acetoin, to the detriment of lactate production.
 ...
PMID:Effect of pyruvate kinase overproduction on glucose metabolism of Lactococcus lactis. 1507 20

In response to combined nitrogen starvation in the growth medium, the filamentous cyanobacterium Anabaena sp. PCC 7120 is able to develop a particular cell type, called a heterocyst, specialized in molecular nitrogen fixation. Heterocysts are regularly intercalated among vegetative cells and represent 5-10% of all cells along each filament. In unicellular cyanobacteria, the key Krebs cycle intermediate, 2-oxoglutarate (2-OG), has been suggested as a nitrogen status signal, but in vivo evidence is still lacking. In this study we show that nitrogen starvation causes 2-OG to accumulate transiently within cells of Anabaena PCC 7120, reaching a maximal intracellular concentration of approximately 0.1 mM 1 h after combined nitrogen starvation. A nonmetabolizable fluorinated 2-OG derivative, 2,2-difluoropentanedioic acid (DFPA), was synthesized and used to demonstrate the signaling function of 2-OG in vivo. DFPA is shown to be a structural analogue of 2-OG and the process of its uptake and accumulation in vivo can be followed by (19)F magic angle spinning NMR because of the presence of the fluorine atom and its chemical stability. DFPA at a threshold concentration of 0.3 mM triggers heterocyst differentiation under repressing conditions. The multidisciplinary approaches using synthetic fluorinated analogues, magic angle spinning NMR for their analysis in vivo, and techniques of molecular biology provide a powerful means to identify the nature of the signals that remain unknown or poorly defined in many signaling pathways.
 ...
PMID:Nonmetabolizable analogue of 2-oxoglutarate elicits heterocyst differentiation under repressive conditions in Anabaena sp. PCC 7120. 1598 52


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>