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 objects of structural studies on biotin-enzymes were acetyl CoA-carboxylase and pyruvate carboxylase of Saccharomyces cerevisiae and beta-methylcrotonyl CoA-carboxylase and acetyl CoA-carboxylase of Achromobacter IV S. It was found that these enzymes can be arranged in three groups. In the first group, as represented by acetyl CoA-carboxylase of Achromobacter, the active enzyme could be resolved in three types of functional components: (1) the biotin-carboxyl carrier protein, (2) the biotin carboxylase, and (3) the carboxyl transferase. In the second group, as represented by beta-methylcrotonyl CoA-carboxylase from Achromobacter only two types of polypeptides are present. The one carries the biotin carboxylase activity together with the biotin-carboxyl-carrier protein, the other one carries the carboxyl transferase activity. In this third group, as represented by the two enzymes of yeast, all three catalytic functions are incorporated in one multifunctional polypeptide chain. The evolution of the different enzymes is discussed. The animal tissues acetyl CoA-carboxylase is under metabolic control, as known from previous studies. It thus has to be expected that the levels of malonyl CoA in livers of rats in all states of depressed fatty acid synthesis are much lower than under normal conditions because the carboxylation of acetyl CoA is strongly reduced and cannot keep pace with the consumption of malonyl CoA by fatty acid synthetase. A new highly sensitive assay method for malonyl CoA was developed which uses tritiated NADPH and measures the incorporation of radioactivity into the fatty acids formed from malonyl CoA in the presence of purified fatty acid synthetase. The application of this method to liver extracts showed that the level of malonyl CoA which amounts to about 7 nmoles per gram of wet liver drops to less than 10% within a starvation period of 24 hr and even further if the starvation period is extended to 48 hr. A low malonyl CoA concentration is also found in the alloxan diabetic animals and in animals being fed a fatty diet after starvation. On the other hand, feeding a carbohydrate rich diet leads to malonyl CoA levels surpassing the levels found after feeding a balanced diet. These observations reconfirm the concept that fatty acid synthesis is principally regulated by the carboxylation of acetyl CoA.
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PMID:New experiments of biotin enzymes. 4 82

The effects of bleomycin upon epithelial DNA synthesis have been evaluated in a keratinizing tissue culture line and following topical application on intact mouse epidermis. In both models, bleomycin inhibited epithelial DNA synthesis after prolonged exposure of the tissue to large doses of the polypeptide antibiotic. The effect is probably limited by the penetration of bleomycin through epithelial cell membranes. Inhibition of epidermal DNA synthesis was also observed in non-treated animals subjected to restraint and/or partial starvation. These conditions, which are commonly associated with studies of topical therapeutic agents, must, therefore, be carefully controlled.
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PMID:Bleomycin: effects upon mammalian epidermal DNA synthesis. 7 1

Mouse sarcoma ascites cells do not utilize fully their capacity for protein synthesis. A considerable portion of their ribosomes occur as inactive monomers. Also, a substantial amount of the cellular mRNA is in the form of ribonucleoprotein particles that sediment in the 20-70S range. This is indicated both by measurements of poly(A) content and by translation of the RNA in cell-free systems. The population of polypeptides synthesized under the direction of the RNA from these particles is less heterogeneous than that directed by RNA from polysomes. The mRNAs for some polypeptides are present predominantly in the small particles. Others are distributed to varying degrees between particles and polysomes. Incubation of the cells with cycloheximide drives most of the ribosomal monomers and a portion of the untranslated mRNA into polysomes. Some of the mRNAs that were predominantly in the inactive fraction seem to be refractory to this treatment. Particles released from polysomes in cells subjected to starvation are quite effective in promoting polypeptide synthesis in a reticulocyte cell-free system and cause the synthesis of a population of polypeptides similar to that coded by the polysomal RNA. The particles from cells exposed to cycloheximide are inactive but yield active RNA upon deproteinization. It is suggested that some mRNA species are maintained in an inactive state in the cell by a component of the nucleoprotein complex.
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PMID:Inactive mRNA-protein complexes from mouse sarcoma-180 ascites cells. 29 64

The translational activity of actively growing microplasmodia and dormant microsclerotia of Physarum polycephalum was investigated by analyzing the distribution of ribosomes in polysomes. Microplasmodial post-mitochondrial fractions contained substantial amounts of polysomes and ribosomal subunits but very few native monosomes. During the starvation period which preceded microsclerotium formation, polysome levels remained constant, whereas the subunit titer began to increase. During encystment ribosomal subunits continued to accumulate as the level of polysomes gradually decreased. Dormant microsclerotia contained a large surplus of stored ribosomal subunits but no detectable polysomes. However, incubation of microsclerotia with concentrations of cycloheximide sufficient to slow polypeptide elongation without affecting initiation caused the gradual reappearance of polysomes at the expense of the subunits. Under these conditions the percentage of subunits driven into polysomes reached values similar to those of actively growing microplasmodia. Microsclerotia returned to nutrient medium contained very low levels of polysomes during the lag period which preceded germination. These were formed with preexisting, stored messenger ribonucleic acid. During the germination period, polysome levels were markedly increased. This elevation was dependent on new ribonucleic acid transcription. It is concluded that dormant microsclerotia contain functional messenger ribonucleic acid and ribosomes which are subject to translational repression at the level of initiation.
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PMID:Translational regulation of polysome formation during dormancy of Physarum polycephalum. 31 5

The amounts of the polypeptide chain elongation factors Tu, Ts, and G, and ribosomal protein SI were assessed under various growth conditions using three independent procedures: (a) Immunoprecipitation and gel electrophoresis, (b) radioimmune assay, and (c) activity measurements. It was demonstrated that, during balanced growth of E. coli, the intracellular levels of these proteins increased in proportion to the growth rate, and the ratio of EF-Tu:EF-Ts:EF-G:protein SI was 4-5:1:1:1, at all growth rates. The effects of isoleucine starvation on the rates of synthesis of these proteins were examined using a pair of isogenic stringent and relaxed strains. The syntheses of all these proteins were found to be under the influence of stringent control. These results indicate that in E. coli the syntheses of the above four proteins are regulated in a coordinated manner and are subject to stringent control.
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PMID:Coordination of levels of elongation factors Tu, Ts, and G, and ribosomal protein SI in Escherichia coli. 34 9

The activity of glycolysis and hexose monophosphate shunt decreases while the activity of some oxydative enzymes and acid phosphatase increases in the anterior pituitary of adult female rats during starvation. The alterations depend on the severity of starvation. The polypeptide hormone production also decreases. A close relationship exists between the metabolic activity of the gland and its endocrine function.
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PMID:Activity alterations of metabolic enzymes in the anterior pituitary of female rats during acute and chronic starvation, as well as after refeeding. 63 63

Insulin, a mitogen for cultured chick embryo fibroblasts (Temin, H.M. (1968) Cancer 3, 771-787), has been employed to characterize the effects of mitogen/cell membrane interactions as it relates to growth. The specific binding of 125I-insulin to substratum-attached cells is time- and temperature dependent and is optimum at a pH of 7.0. Fetal calf and chicken sera, somatomedin "A/C mixed," and desalanine or native porcine insulin compete with 125I-insulin for membrane-binding sites. Proinsulin, although competing less effectively than native insulin for binding, is more effective than desoctapeptide insulin. Unrelated polypeptide hormones do not compete for 125I-insulin binding. The lowest concentration of insulin at which specific binding is detected is 0.1 nM. Scatchard plot analysis of the binding data indicates that there are two types of binding sites in confluent cultures of fibroblasts: one of high affinity (K1 = 2 to 6 X 10(8) M-1) and low capacity, the other of low affinity (K2 = 0.8 to 3.0 X 10(7) M-1) and high capacity. Approximately 1.9 and 7.1 X 10(3) molecules of insulin are bound at each site, respectively. A 10-min incubation at 24 degrees of the fibroblasts with 10 mug/ml of trypsin causes a 2-fold stimulation of specific 125I-insulin binding and a similar 2-fold increase in insulin-stimulated 2-deoxy-D-glucose uptake and thymidine incorporation. Neuraminidase treatment also produces a 37% increase in specific 125I-insulin binding but treatment with alpha-chymotrypsin or phospholipase C are without significant effect. The results of this and additional experiments support the hypothesis that trypsin treatment of chick embryo fibroblasts leads to an unmasking of 125I-insulin binding sites. Serum starvation of fibroblasts for 12 or 24 h produces a 2.5- to 5-fold increase in specific 125I-insulin binding. This increase is the result of an increase in the number of hormone-binding sites from 9 X 10(3) to 6 X 10(4) per cell which are predominantly of the low affinity type. There is no change in the affinity constants. The presence of camptothecin, or cordycepin, or cycloheximide in the incubation medium completely blocks the increase in number of 125I-insulin-binding sites resulting from serum starvation. The addition of native insulin to the medium of serum-starved cultures also blocks this increase. The magnitude of insulin-stimulated 2-deoxy-D-glucose uptake and thymidine incorporation correlates with the levels of occupancy of the low affinity 125I-insulin-binding sites in untreated fibroblasts. In fibroblasts cultured in the absence of serum, the marked increase in insulin-stimulated 2-deoxy-D-glucose uptake and thymidine incorporation parallels the increase in number of mitogen receptors. The concentration of insulin that produces a half-maximum stimulation of thymidine incorporation is calculated to be 5 X 10(-8) M. At this concentration of insulin, 42% of the receptor sites are occupied.
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PMID:Mitogen receptors in chick embryo fibroblasts. Kinetics, specificity, unmasking, and synthesis of 125I-insulin binding sites. 98 22

The GLN1 gene, encoding glutamine synthetase in Saccharomyces cerevisiae, was sequenced, and its encoded polypeptide was shown to have significant homology to other eukaryotic glutamine synthetases. S1 analysis has defined the transcriptional start site of the gene. Upstream analysis of the gene using lacZ fusions has verified transcriptional control of the gene and has identified a nitrogen upstream activation sequence which is required for the increased transcription of GLN1 seen when glutamine is replaced by glutamate as the nitrogen source. cis-acting sites required for the increased transcription in response to purine starvation also have been localized.
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PMID:Sequence of the GLN1 gene of Saccharomyces cerevisiae: role of the upstream region in regulation of glutamine synthetase expression. 134 68

To investigate the role of cilia in mating interactions of Tetrahymena thermophila, ciliary membrane-rich fractions were isolated from two wild-type strains, a non-discharge mucocyst mutant which possesses mating behavior similar to wild-type, and a mating mutant which is able to costimulate cells of complementary mating type but cannot enter into pair formation. In each case, proteins from the ciliary membrane-rich fractions of starved, mating-competent ("initiated") cells were compared with those from non-starved, mating-incompetent ("non-initiated") cells, by gel electrophoresis and lectin blotting. In stained gels, a 43 kDa polypeptide was reduced or absent in initiated cells but present in non-initiated cells, in all strains. In silver-stained gels, a 25 kDa polypeptide was present in all strains, both initiated and non-initiated. In blots probed with Con A-peroxidase, a 25 kDa glycoprotein was present in ciliary membrane fractions from non-initiated cells and absent in membranes of initiated cells of the two wild-type strains and the mucocyst mutant, but is present in initiated and non-initiated cells of the mating mutant (several hypotheses are presented to explain these findings). In addition, ciliary proteins of the mating mutant included at least two unique Con A-binding polypeptides. Our results support the idea that development of mating competence during starvation involves an extensive remodeling of ciliary membranes, and identify a 25 kDa glycoconjugate as having a potential role in control of pair formation during mating.
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PMID:Ciliary polypeptides and glycoconjugates of wild-type and mutant Tetrahymena thermophila: starved versus nonstarved. 139 38

Ornithine decarboxylase (ODC), which initiates the biosynthesis of the polyamines putrescine, spermidine, and spermine, is encoded by the spe-1 gene of the fungus Neurospora crassa. This gene and its cDNA have been cloned and sequenced. The gene has a single 70-nucleotide intron in the coding sequence. The cDNA, comprising the entire coding region, recognizes a single 2.4-kb mRNA in Northern (RNA) blots. The mRNA transcript, defined by S1 mapping, has an extremely long, 535-base leader without strong secondary-structure features or an upstream reading frame. The translational start of the protein is ambiguous: a Met-Val-Met sequence precedes the Pro known to be the N terminus of the ODC polypeptide. The polypeptide encoded by the N. crassa spe-1 gene (484 amino acids) has 46% amino acid identity with that of Saccharomyces cerevisiae (466 amino acids) and 42% with that of mouse (461 amino acids). Alignment of the longer N. crassa sequence with S. cerevisiae and mouse sequences creates gaps in different sites in the S. cerevisiae and mouse sequences, suggesting that N. crassa ODC is closer to an ancestral form of the enzyme than that of either yeast or mouse ODC. N. crassa ODC, which turns over rapidly in vivo in the presence of polyamines, has two PEST sequences, found in most ODCs and other proteins with rapid turnover. In striking contrast to other eucaryotic organisms, the variation in the rate of ODC synthesis in response to polyamines in N. crassa is largely correlated with proportional changes in the abundance of ODC mRNA. Spermidine is the main effector of repression, while putrescine has a weaker effect. However, putrescine accumulation appears to increase the amount of active ODC that is made from a given amount of ODC mRNA, possibly by improving its translatability. Conversely, prolonged starvation for both putrescine and spermidine leads to the differentially impaired translation of ODC mRNA.
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PMID:Ornithine decarboxylase gene of Neurospora crassa: isolation, sequence, and polyamine-mediated regulation of its mRNA. 153 Aug 78


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