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

The alkanesulfonate FMN reductase (SsuE) from Escherichia coli catalyzes the reduction of FMN by NADPH to provide reduced flavin for the monooxygenase (SsuD) enzyme. The vapor-diffusion technique yielded single crystals that grow as hexagonal rods and diffract to 2.9 A resolution using synchrotron X-ray radiation. The protein crystallizes in the primitive hexagonal space group P622. The SsuE protein lacks any cysteine or methionine residues owing to the role of the SsuE enzyme in the acquisition of sulfur during sulfate starvation. Therefore, substitution of two leucine residues (Leu114 and Leu165) to methionine was performed to obtain selenomethionine-containing SsuE for MAD phasing. The selenomethionine derivative of SsuE has been expressed and purified and crystals of the protein have been obtained with and without bound FMN. These preliminary studies should lead to the structure solution of SsuE. It is anticipated that this new protein structure will provide detailed structural information on specific active-site regions of the protein and insight into the mechanism of flavin reduction and transfer of reduced flavin.
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PMID:Crystallization and preliminary X-ray crystallographic studies of the alkanesulfonate FMN reductase from Escherichia coli. 1651 Nov 73

In mammalian cells, MAPKs are involved in both stress response (JNK and p38 pathways) and cell proliferation and differentiation [extracellular signal-regulated kinase (ERK)] through protein kinase cascades. Exposure of Dunaliella viridis cell cultures to PD98059, a very specific inhibitor of the ERK signalling pathway, resulted in a total arrest of cell proliferation and a complete dephosphorylation of ERK. As shown by flow cytometry analysis of propidium iodide-stained cells, PD98059 stopped mitosis at the G(2) phase after the S phase has been completed. Multiple physiological parameters such as cell motility and reducing power generation (NADPH) clearly indicate that the treated cells are wholly viable. Exposure of D. viridis to environmental stresses that impair cell division, such as hyperosmotic shock, nitrogen starvation, or sublethal UV irradiation, caused a marked decrease in the phospho-ERK levels as detected by western blot. Two 400 bp polynucleotides from D. viridis with high homologies to published sequences of ERK1 and ERK2 were cloned, sequenced, and submitted to GenBank. Northern blot analysis revealed two mRNA bands of approximately 1.9 kb, consistent with the expected size of ERK proteins ( approximately 40 kDa). Sequence analysis showed that they contained several mitogen-activated protein kinase (MAPK) conserved domains, including II, III, VIb, VII, and the double phosphorylation motif. Interestingly, in D. viridis, this motif was T*DY* instead of the canonic T*EY*. Based on this finding, ERK plant sequences can be divided into two groups, one termed the T*DY* branch and the other termed the T*EY* branch. The molecular and functional data presented here suggest that ERK is a very ancient signalling pathway and that it was already present in the last common ancestor of all eukaryotic cells.
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PMID:Cell division in the unicellular microalga Dunaliella viridis depends on phosphorylation of extracellular signal-regulated kinases (ERKs). 1722 May 13

The alkanesulfonate monooxygenase system from Escherichia coli is involved in scavenging sulfur from alkanesulfonates under sulfur starvation. An FMN reductase (SsuE) catalyzes the reduction of FMN by NADPH, and the reduced flavin is transferred to the monooxygenase (SsuD). Rapid reaction kinetic analyses were performed to define the microscopic steps involved in SsuE catalyzed flavin reduction. Results from single-wavelength analyses at 450 and 550 nm showed that reduction of FMN occurs in three distinct phases. Following a possible rapid equilibrium binding of FMN and NADPH to SsuE (MC-1) that occurs before the first detectable step, an initial fast phase (241 s(-1)) corresponds to the interaction of NADPH with FMN (CT-1). The second phase is a slow conversion (11 s(-1)) to form a charge-transfer complex of reduced FMNH(2) with NADP(+) (CT-2), and represents electron transfer from the pyridine nucleotide to the flavin. The third step (19 s(-1)) is the decay of the charge-transfer complex to SsuE with bound products (MC-2) or product release from the CT-2 complex. Results from isotope studies with [(4R)-(2)H]NADPH demonstrates a rate-limiting step in electron transfer from NADPH to FMN, and may imply a partial rate-limiting step from CT-2 to MC-2 or the direct release of products from CT-2. While the utilization of flavin as a substrate by the alkanesulfonate monooxygenase system is novel, the mechanism for flavin reduction follows an analogous reaction path as standard flavoproteins.
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PMID:Mechanism of flavin reduction in the alkanesulfonate monooxygenase system. 1728 50

Among the 118 genes upregulated by Pseudomonas aeruginosa in response to iron starvation [Ochsner, U. A., Wilderman, P. J., Vasil, A. I., and Vasil, M. L. (2002) Mol. Microbiol. 45, 1277-1287], we focused on the products of the two genes encoding electron transfer proteins, as a means of identifying the redox partners of the heme oxygenase (pa-HO) expressed under low-iron stress conditions. Biochemical and spectroscopic investigations demonstrated that the bfd gene encodes a 73-amino acid protein (pa-Bfd) that incorporates a [2Fe-2S]2+/+ center, whereas the fpr gene encodes a 258-residue NADPH-dependent ferredoxin reductase (pa-FPR) that utilizes FAD as a cofactor. In vitro reconstitution of pa-HO catalytic activity with the newly characterized proteins led to the surprising observation that pa-FPR efficiently supports the catalytic cycle of pa-HO, without the need of a ferredoxin. In comparison, electron transfer from pa-Bfd to pa-HO is sluggish, which strongly argues against the possibility that the seven electrons needed by pa-HO to degrade biliverdin are transferred from NADPH to pa-HO in a ferredoxin (Bfd)-dependent manner. Given that pa-HO functions to release iron from exogenous heme acquired under iron-starvation conditions, the use of a flavoenzyme rather than an iron-sulfur center-containing protein to support heme degradation is an efficient use of resources in the cell. The crystal structure of pa-FPR (1.6 A resolution) showed that its fold is comparable that of the superfamily of ferredoxin reductases and most similar to the structure of Azotobacter vinelandii FPR and Escherichia coli flavodoxin reductase. The latter two enzymes interact with distinct redox partners, a ferredoxin and a flavodoxin, respectively. Hence, findings reported herein extend the range of redox partners recognized by the fold of pa-FPR to include a heme oxygenase (pa-HO).
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PMID:Biochemical and structural characterization of Pseudomonas aeruginosa Bfd and FPR: ferredoxin NADP+ reductase and not ferredoxin is the redox partner of heme oxygenase under iron-starvation conditions. 1791 50

Malic enzyme catalyzes decarboxylation of malate to pyruvate and CO(2), providing de novo biosynthesis of fatty acids with NADPH. Since lipogenesis in ruminants, contrarily to some monogastric species like human and rodents, occurs predominantly in adipose tissue, the activity of many lipogenic enzymes is higher in adipose tissue compared to liver. Expression of malic enzyme is regulated by nutrition; refeeding after a period of starvation results to an induction of the enzyme. Here we present the nucleotide sequence of two transcripts of the ovine cytosolic malic enzyme gene that differ at the length of the 3' UTR. These are the first published cDNA sequences for ruminant species and share high similarity with the corresponding sequences of other species. Malic enzyme mRNA was present in every ovine tissue that was examined. In agreement with the fact that adipose tissue is the major lipogenic site for ruminants, mRNA levels in adipose tissue were higher than in liver. Refeeding after two weeks of caloric restriction resulted in a two-fold increase of the mRNA level of malic enzyme in adipose tissue.
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PMID:Molecular cloning and characterization of the sheep malic enzyme cDNA. 1867 27

Selenium is an essential micronutrient for humans and animals, and its deficiency can predispose to the development of pathological conditions. This study evaluates the effect of selenium deficiency on the thioredoxin system, consisting of NADPH, selenoprotein thioredoxin reductase (TrxR), and thioredoxin (Trx); and the glutathione system, including NADPH, glutathione reductase, glutathione, and glutaredoxin coupled with selenoprotein glutathione peroxidase (GPx). We particularly investigate whether inactive truncated TrxR is present under selenium-starvation conditions due to reading of the UGA codon as stop. Feeding rats a selenium-deficient diet resulted in a large decrease in activity of TrxR and GPx in rat liver but not in the levels of Trx1 and Grx1. However, selenium deficiency induced mitochondrial Grx2 10-fold and markedly changed the expression of some flavoproteins that are involved in the cellular folate, glucose, and lipid metabolism. Liver TrxR mRNA was nearly unchanged, but no truncated enzyme was found. Instead, a low-activity form of TrxR with a cysteine substituted for the penultimate selenocysteine in the C-terminal active site was identified in selenium-deficient rat liver. These results show a novel mechanism for decoding the UGA stop codon, inserting cysteine to make a full-length enzyme that may be required for selenium assimilation.
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PMID:Penultimate selenocysteine residue replaced by cysteine in thioredoxin reductase from selenium-deficient rat liver. 1935 1

Tumor cells fuel their metabolism with glucose and glutamine to meet the bioenergetic and biosynthetic demands of proliferation. Hypoxia and oncogenic mutations drive glycolysis, with the pyruvate to lactate conversion being promoted by increased expression of lactate dehydrogenase A and inactivation of pyruvate dehydrogenase. The NAD+ pool is consecutively regenerated and supports the high glycolytic flux required to produce anabolic intermediates. Glutaminolysis provides metabolic intermediates such as alpha-ketoglutarate to feed and thereby maintain the tricarboxylic acid cycle as a biosynthetic hub. Glycolysis and glutaminolysis share the capacity to generate NADPH, from the pentose phosphate pathway and through the malate conversion into pyruvate, respectively. Both pathways ultimately lead to the secretion of lactate. More than a waste product, lactate was recently identified as a major energy fuel in tumors. Lactate produced by hypoxic tumor cells may indeed diffuse and be taken up by oxygenated tumor cells. Preferential utilization of lactate for oxidative metabolism spares glucose which may in turn reach hypoxic tumor cells. Monocarboxylate transporter 1 regulates the entry of lactate into oxidative tumor cells. Its inhibition favors the switch from lactate-fuelled respiration to glycolysis and consecutively kills hypoxic tumor cells from glucose starvation. Combination with radiotherapy renders remaining cells more sensitive to irradiation, emphasizing how interference with tumor cell metabolism may complement current anticancer modalities.
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PMID:Pyruvate into lactate and back: from the Warburg effect to symbiotic energy fuel exchange in cancer cells. 1960 89

Although the tricarboxylic acid (TCA) cycle is essential in almost all aerobic organisms, its precise modulation and integration in global cellular metabolism is not fully understood. Here, we report on an alternative TCA cycle uniquely aimed at generating ATP and oxalate, two metabolites critical for the survival of Pseudomonas fluorescens. The upregulation of isocitrate lyase (ICL) and acylating glyoxylate dehydrogenase (AGODH) led to the enhanced synthesis of oxalate, a dicarboxylic acid involved in the immobilization of aluminum (Al). The increased activity of succinyl-CoA synthetase (SCS) and oxalate CoA-transferase (OCT) in the Al-stressed cells afforded an effective route to ATP synthesis from oxalyl-CoA via substrate level phosphorylation. This modified TCA cycle with diminished efficacy in NADH production and decreased CO(2)-evolving capacity, orchestrates the synthesis of oxalate, NADPH, and ATP, ingredients pivotal to the survival of P. fluorescens in an Al environment. The channeling of succinyl-CoA towards ATP formation may be an important function of the TCA cycle during anaerobiosis, Fe starvation and O(2)-limited conditions.
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PMID:An ATP and oxalate generating variant tricarboxylic acid cycle counters aluminum toxicity in Pseudomonas fluorescens. 1980 98

Mono-ADP-ribosylation is the enzymatic transfer of ADP-ribose from NAD(+) to acceptor proteins catalyzed by ADP-ribosyltransferases. Using m-aminophenylboronate affinity chromatography, 2D-gel electrophoresis, in-gel digestion and MALDI-TOF analysis we have identified eight in vitro ADP-ribosylated proteins in Streptomyces coelicolor, which can be classified into three categories: (i) secreted proteins; (ii) metabolic enzymes using NAD(+)/NADH or NADP(+)/NADPH as coenzymes; and (iii) other proteins. The secreted proteins could be classified into two functional categories: SCO2008 and SC05477 encode members of the family of periplasmic extracellular solute-binding proteins, and SCO6108 and SC01968 are secreted hydrolases. Dehydrogenases are encoded by SC04824 and SC04771. The other targets are GlnA (glutamine synthetase I., SC02198) and SpaA (starvation-sensing protein encoded by SC07629). SCO2008 protein and GlnA had been identified as ADP-ribosylated proteins in previous studies. With these results we provided experimental support for a previous suggestion that ADP-ribosylation may regulate membrane transport and localization of periplasmic proteins. Since ADP-ribosylation results in inactivation of the target protein, ADP-ribosylation of dehydrogenases might modulate crucial primary metabolic pathways in Streptomyces. Several of the proteins identified here could provide a strong connection between protein ADP-ribosylation and the regulation of morphological differentiation in S. coelicolor.
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PMID:Analysis and identification of ADP-ribosylated proteins of Streptomyces coelicolor M145. 1985 27

The comparative study of expression of early c-fos-gene (marker of neuronal activation) and NADPH-diaphorase reactivity (NADPH-dr) was performed in the cervical spinal cord of rats in the control (intact) animal, in the state of starvation and after realization of long-lasting (repeated 4 to 12 times per minute for 30 min) motivated stereotyped food-procuring forelimb movements. In comparison with control rats; in the starving rats or rats showed forelimb movement to reach-to-grasp the food, the number of Fos-immunoreactive (Fos-ir) cells in the dorsal and ventral horns of a 40-microm-thick slice was significantly greater (P < 0.05). The number of Fosir neurons in the starving state clearly exceeded that in the most layers after realization of movements. Increase of Fos immunoreactivity in the superficial (2i, 3) and deeper (4, 5) layers of the dorsal horn was initiated, evidently, by signals from peripheral and supraspinal structures. We also found labelled cells within layers 6-8, and 9 demonstrating the activity of interneurons and motoneurons directly involved into generation of operant forelimb movements. According to our data, high density of NADPH-dr/NO-generating neurons in the C6/C7 segments are observed in the substance gelatinosa (layer 2i) and layers 7 and 10. NADPH-dr cells and Fos-ir neurons were intermixed within the layers but did not demonstrate double-labelling. It is possible to suggest that NADPH-dr/NO-generating cells of the spinal cord did not operate under realization of the studied operant reflexes, which did not include nociceptive component.
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PMID:[Laminar distribution of the active spinal cord neurons during the feeding-related stereotyped movements in the rat]. 2096 41


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