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

In Saccharomyces cerevisiae, signal transduction through pathways governing mating, osmoregulation, and nitrogen starvation depends upon a direct interaction between the sterile alpha motif (SAM) domains of the Ste11 mitogen-activated protein kinase kinase kinase (MAPKKK) and its regulator Ste50. Previously, we solved the NMR structure of the SAM domain from Ste11 and identified two mutants that diminished binding to the Ste50 SAM domain. Building upon the Ste11 study, we present the NMR structure of the monomeric Ste50 SAM domain and a series of mutants bearing substitutions at surface-exposed hydrophobic amino acid residues. The mid-loop (ML) region of Ste11-SAM, defined by helices H3 and H4 and the end-helix (EH) region of Ste50-SAM, defined by helix H5, were sensitive to substitution, indicating that these two surfaces contribute to the high-affinity interaction. The combination of two mutants, Ste11-SAM-L72R and Ste50-SAM-L69R, formed a high-affinity heterodimer unencumbered by competing homotypic interactions that had prevented earlier NMR studies of the wild-type complex. Yeast bearing mutations that prevented the heterotypic Ste11-Ste50 association in vitro presented signaling defects in the mating and high-osmolarity growth pathways.
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PMID:Saccharomyces cerevisiae Ste50 binds the MAPKKK Ste11 through a head-to-tail SAM domain interaction. 1633 30

Vpx facilitates HIV-2 nuclear localization by a poorly understood mechanism. We have compared Vpx to an NMR structure HIV-1 Vpr in a central helical domain and probed regions of Vpx by insertional mutagenesis. A predicted loop between helices two and three appears to be unique, overlapping with a known novel nuclear localization signal. Overall, Vpx was found to be surprisingly flexible, tolerating a series of large insertions. We found that insertion within the polyproline-containing C-terminus destabilizes nuclear localization, whereas mutating a second helix in the central domain disrupts viral packaging. Other insertional mutants in the predicted loop and in a linker region between the central domain and the C-terminus may be useful as sites of intramolecular tags as they could be packaged adequately and retained preintegration complex associated integration activity in a serum starvation assay. An unexpected result was found within a previously defined nuclear localization motif near aa 71. This mutant retained robust nuclear localization in a GFP fusion assay and was competent for preintegration complex associated nuclear import. In summary, we have modeled helical content in Vpx and assessed potential sites of intramolecular tags which may prove useful for protein-protein interactions studies.
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PMID:Analysis of HIV-2 Vpx by modeling and insertional mutagenesis. 1645 68

Sugars, the main growth substrates of plants, act as physiological signals in the complex regulatory network of sugar metabolism. To investigate the function of different glycolytic steps in sugar sensing and signaling we compared the effects of carbon starvation with those of glucose, glycerol and dihydroxyacetone on carbon metabolism, proteolysis, and protease expression in excised maize (Zea mays L.) root tips. Respiration, soluble proteins, protein turnover and proteolytic activities were monitored as a function of time, along with in vitro and in vivo analysis of a variety of metabolites (sugars, amino and organic acids, phosphoesters, adenine nucleotides...) using (13)C, (31)P and (1)H NMR spectroscopy. Our results indicate that, in maize root tips, endopeptidase activities and protease expression are induced in response to a decrease in carbon supply to the upper part of the glycolytic pathway, i.e. at the hexokinase step. Proteolysis would be controlled downstream glycolysis, probably at the level of the respiratory substrate supply to mitochondria.
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PMID:A metabolic study of the regulation of proteolysis by sugars in maize root tips: effects of glycerol and dihydroxyacetone. 1694 97

Burn trauma is a clinical condition accompanied by muscle wasting that severely impedes rehabilitation in burn survivors. Mitochondrial uncoupling protein 3 (UCP3) is uniformly expressed in myoskeletal mitochondria and its expression has been found to increase in other clinical syndromes that, like burn trauma, are associated with muscle wasting (e.g., starvation, fasting, cancer, sepsis). The aim of this study was to explore the effects of burn trauma on UCP3 expression, intramyocellular lipids, and plasma-free fatty acids. Mice were studied at 6 h, 1 d and 3 d after nonlethal hindlimb burn trauma. Intramyocellular lipids in hindlimb skeletal muscle samples collected from burned and normal mice were measured using 1H NMR spectroscopy on a Bruker 14.1 Tesla spectrometer at 4 degrees C. UCP3 mRNA and protein levels were also measured in these samples. Plasma-free fatty acids were measured in burned and normal mice. Local burn trauma was found to result in: 1) upregulation of UCP3 mRNA and protein expression in hindlimb myoskeletal mitochondria by 6 h postburn; 2) increased intramyocellular lipids; and 3) increased plasma-free fatty acids. Our findings show that the increase in UCP3 after burn trauma may be linked to burn-induced alterations in lipid metabolism. Such a link could reveal novel insights into how processes related to energy metabolism are controlled in burn and suggest that induction of UCP3 by burn in skeletal muscle is protective by either activating cellular redox signaling and/or mitochondrial uncoupling.
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PMID:Uncoupling protein 3 expression and intramyocellular lipid accumulation by NMR following local burn trauma. 1708 30

Uptake and metabolism of silicon by diatoms are studied by the combined use of solid-state 29Si NMR spectroscopy and confocal laser fluorescence microscopy especially with respect to the presence and nature of an intracellular silicon-storage pool. Cells of the marine diatom Thalassiosira pseudonana were synchronized by silicon starvation and frozen without any freeze-drying or chemical treatment in order to analyze integer and unmodified diatoms. The frozen samples were investigated by solid-state 29Si NMR spectroscopy to identify potential silica precursors. The developmental state of the cell culture and the formation of new siliceous girdle bands and valves were monitored by laser fluorescence microscopic studies. A comparison of fluorescence microscopic and NMR data allows the assignment of NMR spectra to the various developmental stages of the dividing diatom cells. A detailed analysis of solid-state 29Si NMR spectra suggests that the silicon-storage pool-if present-consists of four-coordinated, condensed silicon; possibly a silica sol.
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PMID:Silicon uptake and metabolism of the marine diatom Thalassiosira pseudonana: Solid-state 29Si NMR and fluorescence microscopic studies. 1795 90

Metabolic flux analysis indicated that the heterofermentative Lactobacillus reuteri strain ATCC 55730 uses both the Embden-Meyerhof pathway (EMP) and phosphoketolase pathway (PKP) when glucose or sucrose is converted into the three-carbon intermediate stage of glycolysis. In all cases studied, the main flux is through the PKP, while the EMP is used as a shunt. In the exponential growth phase, 70%, 73%, and 84% of the flux goes through the PKP in cells metabolizing (i) glucose plus fructose, (ii) glucose alone, and (iii) sucrose alone, respectively. Analysis of the genome of L. reuteri ATCC 55730 confirmed the presence of the genes for both pathways. Further evidence for the simultaneous operation of two central carbon metabolic pathways was found through the detection of fructose-1,6-bisphosphate aldolase, phosphofructokinase, and phosphoglucoisomerase activities and the presence of phosphorylated EMP and PKP intermediates using in vitro 31P NMR. The maximum specific growth rate and biomass yield obtained on glucose were twice as low as on sucrose. This was the result of low ATP levels being present in glucose-metabolizing cells, although the ATP production flux was as high as in sucrose-metabolizing cells due to a twofold increase of enzyme activities in both glycolytic pathways. Growth performance on glucose could be improved by adding fructose as an external electron acceptor, suggesting that the observed behavior is due to a redox imbalance causing energy starvation.
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PMID:Phosphoketolase pathway dominates in Lactobacillus reuteri ATCC 55730 containing dual pathways for glycolysis. 1796 51

Learning and memory are essential processes of both vertebrate and invertebrate nervous systems that allow animals to survive and reproduce. The neurotransmitter glutamate signals via ionotropic glutamate receptors (iGluRs) that have been linked to learning and memory formation; however, the signaling pathways that contribute to these behaviors are still not well understood. We therefore undertook a genetic and electrophysiological analysis of learning and memory in the nematode Caenorhabditis elegans. Here, we show that two genes, nmr-1 and nmr-2, are predicted to encode the subunits of an NMDA-type (NMDAR) iGluR that is necessary for memory retention in C. elegans. We cloned nmr-2, generated a deletion mutation in the gene, and showed that like nmr-1, nmr-2 is required for in vivo NMDA-gated currents. Using an associative-learning paradigm that pairs starvation with the attractant NaCl, we also showed that the memory of a learned avoidance response is dependent on NMR-1 and NMR-2 and that expression of NMDARs in a single pair of interneurons is sufficient for normal memory. Our results provide new insights into the molecular and cellular mechanisms underlying the memory of a learned event.
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PMID:Memory in Caenorhabditis elegans is mediated by NMDA-type ionotropic glutamate receptors. 1858 34

In filamentous fungi, the GATA-type transcription factor AreA plays a major role in the transcriptional activation of genes needed to utilize poor nitrogen sources. In Fusarium fujikuroi, AreA also controls genes involved in the biosynthesis of gibberellins, a family of diterpenoid plant hormones. To identify more genes responding to nitrogen limitation or sufficiency in an AreA-dependent or -independent manner, we examined changes in gene expression of F. fujikuroi wild-type and DeltaareA strains by use of a Fusarium verticillioides microarray representing approximately 9,300 genes. Analysis of the array data revealed sets of genes significantly down- and upregulated in the areA mutant under both N starvation and N-sufficient conditions. Among the downregulated genes are those involved in nitrogen metabolism, e.g., those encoding glutamine synthetase and nitrogen permeases, but also those involved in secondary metabolism. Besides AreA-dependent genes, we found an even larger set of genes responding to N starvation and N-sufficient conditions in an AreA-independent manner. To study the impact of NMR on AreA activity, we examined the expression of several AreA target genes in the wild type and in areA and nmr deletion and overexpression mutants. We show that NMR interacts with AreA as expected but affects gene expression only in early growth stages. This is the first report on genome-wide expression studies examining the influence of AreA on nitrogen-responsive gene expression in a genome-wide manner in filamentous fungi.
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PMID:Cross-species hybridization with Fusarium verticillioides microarrays reveals new insights into Fusarium fujikuroi nitrogen regulation and the role of AreA and NMR. 1868 24

Ornamental tobacco (Nicotiana alata) produces a series of 6 kDa proteinase inhibitors belonging to the potato type II inhibitor family. These proteins inhibit trypsin and chymotrypsin, the main digestive enzymes of predatory insects, thus leading to starvation, impaired larval development or death. In this context, the three-dimensional structures of these inhibitors are important for developing novel strategies for pest control. The solution structures of C1 and T1, the two main prototypes of the N. alata inhibitors, were originally determined more than a decade ago (J. Mol. Biol. 242, 231-243 (1994) and Biochemistry 34, 14304-14311 (1995)). Since then methods for NMR structure calculations have evolved considerably. Here we report the refinement of the structures of C1 and T1 with state-of-the-art protocols for NMR structure calculations. This refinement leads to an improved quality of the structures, making them a more reliable basis for the development of novel pesticides and modeling applications.
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PMID:Structural refinement of insecticidal plant proteinase inhibitors from Nicotiana alata. 1899 65

GSP13 encoded by gene yugI is a sigma(B)-dependent general stress protein in Bacillus subtilis, which can be induced by heat shock, salt stress, ethanol stress, glucose starvation, oxidative stress and cold shock. Here we report the solution structure of GSP13 and it is the first structure of S1 domain containing protein in Bacillus subtilis. The structure of GSP13 mainly consists of a typical S1 domain along with a C-terminal 50-residue flexible tail, different from the other known S1 domain containing proteins. Comparison with other S1 domain structures reveals that GSP13 has a conserved RNA binding surface, and it may function similarly to cold shock proteins in response to cold stress.
J Biomol NMR 2009 Apr
PMID:Solution structure of GSP13 from Bacillus subtilis exhibits an S1 domain related to cold shock proteins. 1915 54


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