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)

Brucella abortus grown in low-iron medium or in the presence of iron chelators [ethylenediamine-di(o-hydroxyphenylacetic acid) and 2,2-dipyridyl] showed reduced cell yields and released a material positive in chemical and biological assays for catechols. This material was purified from culture fluids of B. abortus 2308 by chromatography on agarose-iminodiacetic acid-Fe3+ and identified as 2,3-dihydroxybenzoic acid (2,3-DHBA) by thin-layer chromatography, paper electrophoresis, and UV-visible nuclear magnetic resonance and mass spectroscopy. No other major catechols were observed at different stages of growth, and 2,3-DHBA was also produced upon iron limitation by representative strains of B. abortus biotypes 1, 5, 6, and 9. Both synthetic 2,3-DHBA and the natural catechol relieved the growth inhibition of B. abortus 2308 by ethylenediamine-di(o-hydroxyphenylacetic acid), and 2,3-DHBA promoted 55Fe uptake by B. abortus 2308 by an energy-dependent mechanism. Two other monocatechols tested, 2,3-dihydroxybenzoyl-Ser and 2,3-dihydroxybenzoyl-Gly, also promoted 55Fe uptake. More complex catechol siderophores (agrobactin and enterobactin), hydroxamate siderophores (aerobactin, ferrichrome, and deferriferrioxamine mesylate [Desferal]), and an EDTA-related siderophore (rhizobactin) failed to mediate 55Fe uptake. B. abortus cells grown in low-iron medium or in medium with iron had similar rates of iron uptake when supplied with 55Fe-2,3-DHBA, and the release of 2,3-DHBA under iron starvation was not associated with the expression of new outer membrane proteins. These results suggest an uptake system in which only the synthesis of the siderophore is regulated by the iron available for growth.
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PMID:Identification of 2,3-dihydroxybenzoic acid as a Brucella abortus siderophore. 139 64

The isoform of cytochrome P450 that catalyzes the 12 alpha-hydroxylation of 7 alpha-hydroxy-4-cholesten-3-one, an intermediate in the conversion of cholesterol to cholic acid, was purified to homogeneity from rabbit liver microsomes. The extent of purification in the various steps was judged by an assay involving high performance liquid chromatography. The purified enzyme showed a single band on SDS-polyacrylamide gel electrophoresis (M(r) = 50,000). The NH2-terminal amino acid sequence is as follows: Val-Leu-Trp-Gly-Leu-Leu-Gly-Ala-Leu-Leu-Met-Val-Met-Val-Gly-, which is different from that of any other P450s so far reported. The specific content of the enzyme was 13.3 nmol of cytochrome P450/mg of protein. Upon reconstitution with NADPH-cytochrome P450 reductase and cytochrome b5, the P450 enzyme showed a high activity of 12 alpha-hydroxylation with a turnover number of 36.6 min-1 at 37 degrees C. The omission of either cytochrome P450 or NADPH-cytochrome P450 reductase resulted in complete loss of activity, and the omission of cytochrome b5 resulted in 40% loss of activity. Antibodies prepared from mouse inhibited the 12 alpha-hydroxylase activity of rabbit liver microsomes about 90% and that of the rat liver microsomes 50%. The enzyme activity was not inhibited by other antibodies raised against other forms of P450 that catalyze different monooxygenation reactions toward xenobiotics or endogenous substrates. Anti-cytochrome b5 antibody inhibited the activity 40%, suggesting the functional role of this protein, and anti-reductase inhibited the activity almost completely. The microsomal enzyme activity was markedly elevated by starvation or streptozotocin administration to the animals. However, an immunoblotting experiment showed no correlation between the enzyme activity and the amount of protein, suggesting that post-translational modification may occur.
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PMID:Purification and characterization of 7 alpha-hydroxy-4-cholesten-3-one 12 alpha-hydroxylase. 140 Apr 44

We have investigated the relative contribution of hydrolysis, intact transport and urinary excretion to the renal clearance of Gly-Sar, Gly-Sar-Sar, and Gly-Gly-Sar in fed and starved rats. The results obtained from isolated kidney perfusion studies are summarized as follows: 1) clearance was fastest for Gly-Gly-Sar and slowest for Gly-Sar-Sar, 2) urinary excretion of Gly-Sar-Sar exceeded that of Gly-Gly-Sar or Gly-Sar, 3) there was accumulation of products of hydrolysis of Gly-Gly-Sar in the perfusate but not of Gly-Sar or Gly-Sar-Sar, 4) isolated brush-border and basolateral membranes of renal tubular cells lacked hydrolytic activity against Gly-Sar and Gly-Sar-Sar but possessed hydrolytic activity against Gly-Gly-Sar, 5) an excess amount of Gly-Sar-Sar reduced the rate of clearance of Gly-Gly-Sar by approximately 40% and significantly increased urinary excretion of this peptide, 6) the nonfiltering kidney cleared Gly-Gly-Sar at a rate which was 50% of that of the filtering kidney but did not clear Gly-Sar, and 7) starvation for 96 h was without a significant effect on the renal clearance of either Gly-Sar or Gly-Sar-Sar but significantly reduced the renal clearance of Gly-Gly-Sar and the brush-border membrane hydrolase activity against this peptide. We conclude that the molecular structure determines the affinity of oligopeptides for the membrane transport and hydrolytic systems, which, in turn, determines their efficiency for clearance by the kidney.
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PMID:Oligopeptides: mechanism of renal clearance depends on molecular structure. 163 35

Na(+)-dependent L-Alanine and Glycine uptake by rat red blood cells were best fit to a common model of two transport components, saturable transport and diffusion. 24 hours of food deprivation provoked statistically significant increases of the Km and Vmax red cells L-Alanine uptake, whereas the diffusion constant did not change in response to starvation. The Glycine uptake kinetics poorly follows the L-Alanine pattern and no significant response to starvation can be outlined. The physiological meaning of these adaptations has to be related to short term food deprivation regulation, independent of protein synthesis in the erythrocytes. Such mechanisms could be important to account for the previously described changes in the distribution patterns of amino acids between the blood plasma and blood cell compartments in response to short term starvation.
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PMID:Short term starvation-induced changes in the kinetic parameters of rat red cell L-alanine and glycine uptake. 181 Feb 54

Plasma membrane vesicles prepared from intact rat liver or isolated hepatocytes retain transport activity by systems A, ASC, N, and Gly. Selective substrates for these systems showed a Na+-dependent overshoot indicative of energy-dependent transport, in this instance, driven by an artificially-imposed Na+ gradient. Greater than 85% of Na+-dependent 2-aminoisobutyric acid (AIB) uptake was blocked by an excess of 2-(methylamino)isobutyric acid (MeAIB) with an apparent Ki of 0.6 mM. Intact hepatocytes obtained from glucagon-treated rats exhibited a stimulation of system A activity and plasma membrane vesicles isolated from those same cells partially retained the elevated activity. Transport activity induced by substrate starvation of cultured hepatocytes was also evident in membrane vesicles prepared from those cells. The membrane-bound glucagon-stimulated system A activity decays rapidly during incubation of vesicles at 4 degrees C (t1/2 = 13 h), but not at -75 degrees C. Several different inhibitors of proteolysis were ineffective in blocking the decay of transport activity. Hepatic system N transport activity was also elevated in plasma membrane vesicles from glucagon-treated rats, whereas system ASC was essentially unchanged. The results indicate that both glucagon and adaptive regulation cause an induction of amino acid transport through a plasma membrane-associated protein.
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PMID:Maintenance of glucagon-stimulated system A amino acid transport activity in rat liver plasma membrane vesicles. 396 88

The purpose of this study was to investigate the mechanisms involved in the reduced thyroid function in starved, young female rats. Food deprivation for 3 days reduced the hypothalamic content of prothyrotrophin-releasing hormone (proTRH) mRNA, the amount of proTRH-derived peptides (TRH and proTRH160-169) in the paraventricular nucleus, the release of proTRH-derived peptides into hypophysial portal blood and the pituitary levels of TSH beta mRNA. Plasma TSH was either not affected or slightly reduced by starvation, but food deprivation induced marked increases in plasma corticosterone and decreases in plasma thyroid hormones. Refeeding after starvation normalized these parameters. Since the molar ratio of TRH and proTRH160-169 in hypophysial portal blood was not affected by food deprivation, it seems unlikely that proTRH processing is altered by starvation. The median eminence content of pGlu-His-Pro-Gly (TRH-Gly, a presumed immediate precursor of TRH), proTRH160-169 or TRH were not affected by food deprivation. Since median eminence TRH-Gly levels were very low compared with other proTRH-derived peptides it is unlikely that alpha-amidation is a rate-limiting step in hypothalamic TRH synthesis. Possible negative effects of the increased corticosterone levels during starvation on proTRH and TSH synthesis were studied in adrenalectomized rats which were treated with corticosterone in their drinking water (0.2 mg/ml). In this way, the starvation-induced increase in plasma corticosterone could be prevented. Although plasma levels of thyroid hormones remained reduced, food deprivation no longer had negative effects on hypothalamic proTRH mRNA, pituitary TSH beta mRNA and plasma TSH in starved adrenalectomized rats. Thus, high levels of corticosteroids seem to exert negative effects on the synthesis and release of proTRH and TSH. This conclusion is corroborated by the observation that TRH release into hypophysial portal blood became reduced after administration of the synthetic glucocorticosteroid dexamethasone. On the basis of these results, it is suggested that the reduced thyroid function during starvation is due to a reduced synthesis and release of TRH and TSH. Furthermore, the reduced TRH and TSH synthesis during food deprivation are probably caused by the starvation-induced enhanced adrenal secretion of corticosterone.
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PMID:Starvation-induced changes in the hypothalamic content of prothyrotrophin-releasing hormone (proTRH) mRNA and the hypothalamic release of proTRH-derived peptides: role of the adrenal gland. 779 20

Glycine was transported in Fusarium oxysporum cells, grown on glycine as the sole source of carbon and nitrogen, by a facilitated diffusion transport system with a half-saturation constant (Ks) of 11 mM and a maximum velocity (Vmax) of 1.2 mM (g dry weight)-1 h-1 at pH 5.0 and 26 degrees C. Under conditions of nitrogen starvation, the same system was present together with a high-affinity one (Ks) of about 47 microM and Vmax of about 60 microM (g dry weight)-1 h-1). The low-affinity system was more specific than the high-affinity system. Cells grown on gelatine showed the same behavior. In cells grown on glucose-gelatine medium, the low-affinity system was poorly expressed even after carbon and nitrogen starvation. Moreover, addition of glucose to cells grown on glycine and resuspended in mineral medium caused an increase of the glycine transport probably due to a boost in protein synthesis. This stimulation did not affect the Ks of the low-affinity system. These results demonstrate that, as is the case for other eukaryotic systems, F. oxysporum glycine transport is under control of nitrogen sources but its regulation by carbon sources appears to be more complex.
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PMID:Characterization and regulation of glycine transport in Fusarium oxysporum var. lini. 918 Oct 75

Mt4 is a cDNA representing a phosphate-starvation-inducible gene from Medicago truncatula that is down-regulated in roots in response to inorganic phosphate (Pi) fertilization and colonization by arbuscular mycorrhizal fungi. Split-root experiments revealed that the expression of the Mt4 gene in M. truncatula roots is down-regulated systemically by both Pi fertilization and colonization by arbuscular mycorrhizal fungi. A comparison of Pi levels in these tissues suggested that this systemic down-regulation is not caused by Pi accumulation. Using a 30-bp region of the Mt4 gene as a probe, Pi-starvation-inducible Mt4-like genes were detected in Arabidopsis and soybean (Glycine max L.), but not in corn (Zea mays L.). Analysis of the expression of the Mt4-like Arabidopsis gene, At4, in wild-type Arabidopsis and pho1, a mutant unable to load Pi into the xylem, suggests that Pi must first be translocated to the shoot for down-regulation to occur. The data from the pho1 and split-root studies are consistent with the presence of a translocatable shoot factor responsible for mediating the systemic down-regulation of Mt4-like genes in roots.
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PMID:The down-regulation of Mt4-like genes by phosphate fertilization occurs systemically and involves phosphate translocation to the shoots. 988 Mar 66

Autophagy is a process that involves the bulk degradation of cytoplasmic components by the lysosomal/vacuolar system. In the yeast, Saccharomyces cerevisiae, an autophagosome is formed in the cytosol. The outer membrane of the autophagosome is fused with the vacuole, releasing the inner membrane structure, an autophagic body, into the vacuole. The autophagic body is subsequently degraded by vacuolar hydrolases. Taking advantage of yeast genetics, apg (autophagy-defective) mutants were isolated that are defective in terms of formation of autophagic bodies under nutrient starvation conditions. One of the APG gene products, Apg12p, is covalently attached to Apg5p via the C-terminal Gly of Apg12p as in the case of ubiquitylation, and this conjugation is essential for autophagy. Apg7p is a novel E1 enzyme essential for the Apg12p-conjugation system. In mammalian cells, the human Apg12p homolog (hApg12p) also conjugates with the human Apg5p homolog. In this study, the unique characteristics of hApg7p are shown. A two-hybrid experiment indicated that hApg12p interacts with hApg7p. Site-directed mutagenesis revealed that Cys(572) of hApg7p is an authentic active site cysteine residue essential for the formation of the hApg7p.hApg12p intermediate. Overexpression of hApg7p enhances the formation of the hApg5p.hApg12p conjugate, indicating that hApg7p is an E1-like enzyme essential for the hApg12p conjugation system. Cross-linking experiments and glycerol-gradient centrifugation analysis showed that the mammalian Apg7p homolog forms a homodimer as in yeast Apg7p. Each of three human Apg8p counterparts, i.e. the Golgi-associated ATPase enhancer of 16 kDa, GABA(A) receptor-associated protein, and microtubule-associated protein light chain 3, coimmunoprecipitates with hApg7p and conjugates with mutant hApg7p(C572S) to form a stable intermediate via an ester bond. These results indicate that hApg7p is an authentic protein-activating enzyme for hApg12p and the three Apg8p homologs.
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PMID:The human homolog of Saccharomyces cerevisiae Apg7p is a Protein-activating enzyme for multiple substrates including human Apg12p, GATE-16, GABARAP, and MAP-LC3. 1109 62

The rplK gene of Corynebacterium glutamicum ATCC13032 comprises 438 nucleotides and encodes a protein of 145 amino acids with a molecular mass of 15.3 kDa. The amino acid sequence revealed extensive similarities to the large ribosomal subunit protein L11 from several Gram-positive and Gram-negative bacteria. The C. glutamicum rplK gene is located downstream of secE, representing part of the protein export apparatus, and of nusG, encoding a transcription antiterminator protein. The rplK gene is followed by an ORF homologous to rplA encoding the 50S ribosomal protein L1. Northern analysis revealed that transcription of the rplK-rplA cluster resulted in two different transcripts of 1.5 and 0.6 kb. The 1.5 kb transcript corresponds to the entire rplK-rplA cluster and the short transcript originates from the rplK gene. A C. glutamicum rplK mutant strain carrying a 12 bp in-frame deletion within rplK, which resulted in the loss of the tetrapeptide Pro-Ala-Leu-Gly in the L11 protein, was constructed. The mutant failed to accumulate (p)ppGpp in response to amino acid starvation and exhibited an increased tolerance to the antibiotic thiostrepton. Evidently, the C. glutamicum rplK gene is required for (p)ppGpp accumulation upon nutritional starvation.
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PMID:A Corynebacterium glutamicum mutant with a defined deletion within the rplK gene is impaired in (p)ppGpp accumulation upon amino acid starvation. 1123 76


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