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 involvement of undermodified tRNA in the regulation of the ilvGEDA operon has been investigated using Escherichia coli C6, a relA-, Cys-, Met- mutant. This strain accumulates thionucleotide-deficient or methyl-deficient tRNA when starved for cysteine or methionine, respectively. The levels of threonine deaminase, the ilvA gene product, and transaminase B, the ilvE gene product, were both lower in cysteine-starved cells, as compared with either growing or methionine-starved cultures. When cysteine was added to cysteine-starved cells, growth ensued promptly and both enzyme activities returned to control levels. Treatment of recovering cultures with valine limited growth by isoleucine limitation, but did not cause a derepression of the ilvGEDA operon. Valine treatment of nonstarved or methionine-starved cells led to the expected increase in threonine deaminase and transaminase B activities. Cysteine-starved cells slowly regained the ability to derepress the operon after 3 h of recovery in complete medium. In contrast, the induction of the lac operon was normal in cysteine-starved cultures, even in the presence of valine. The loss of derepressibility of the ilvGEDA operon was correlated with the presence of a kinetically and chromatographically altered tRNAIle in cysteine-starved cells. No changes in tRNAIle were observed after methionine starvation. Using the periodate method, we found that the charging of tRNAIle increased from the normal level of 60 to 80% or greater after starvation for cysteine. Under conditions where the ilvGEDA operon was fully derepressed in nonstarved cells, the charging of tRNAIle fell to 27%. Unexpectedly, nearly identical results were obtained with cysteine-starved cells after an identical derepression test. These results suggest that factors other than the aminoacylation state of tRNAIle may be important in the regulation of this operon. In particular, modifications to tRNA which involve cysteine may be necessary for controlling the expression of the ilvGEDA operon in E. coli.
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PMID:Cysteine starvation, isoleucyl-tRNAIle, and the regulation of the ilvGEDA operon of Escherichia coli. 634 28

The effect of amino acid starvation on the accuracy of translation of ribosomal proteins was analyzed in a stringent (relA+)/relaxed (relA) pair of E. coli strains. The degree of misreading was estimated from the amount of cysteine erroneously incorporated into individual proteins during arginine starvation of bacteria. Illegitimate incorporation of cysteine was found to occur to a significant extent in several proteins from both the small and the large subunits of ribosomes, in either type of strain.
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PMID:Erroneous synthesis of ribosomal proteins in amino acid starved E. coli. 636 97

A cysteine metalloproteinase that degrades 125I-insulin B chain at neutral pH values was isolated from C3H mouse liver. The enzyme was partially purified from the 100,000g supernatant fraction by ammonium sulfate precipitation, DEAE-cellulose chromatography, and fast protein liquid chromatography. The molecular weight of the proteinase was estimated to be 190,000 by gel filtration on Sephadex G-200. Degradation of 125I-insulin B chain by the proteinase was inhibited by p-hydroxymercuribenzoate (PHMB) and iodoacetate (cysteine proteinase inhibitors) and by ethylenediaminetetraacetic acid (EDTA) and 1,10-phenanthroline (metalloproteinase inhibitors). The proteinase also degraded 125I-glucagon but did not hydrolyze 125I-insulin, leucine-2-naphthylamide, or several large proteins. Equivalent levels of EDTA- and PHMB-inhibitable 125I-insulin B chain-degrading activity were observed in the 100,000g supernatant fractions of brain, liver, lung, kidney, heart, and spleen from four mouse strains (C3H/HeN, CBA/J, ICR, and C57BL/6). High levels of 125I-insulin B chain-degrading activity were found in the particulate fraction of kidneys and lungs from these four mouse strains; these activities were inhibited by EDTA but not by PHMB. The activity of the soluble liver cysteine metalloproteinase was not altered in C3H mice treated ip with metal chelators, bacterial endotoxin, phenobarbital, dexamethasone, or insulin. Starvation for 24 or 48 hr and alloxan-induced diabetes diminished total activity of this enzyme in liver by about 50 and 30%, respectively. This soluble polypeptide-degrading enzyme appears to be ubiquitous in mice and to be regulated by nutritional conditions.
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PMID:A cysteine metalloproteinase from mouse liver cytosol. 643 52

To elucidate the recently advanced hypothesis that glutathione [L-gamma-glutamyl-L-cysteinyl glycine (GSH)] regulates deiodinating enzyme activities, accounting for the decreased conversion of T4 to T3 in the liver of fetal and starved animals, we investigated thyroid hormone metabolism in GSH-depleted neoplastic and normal hepatocytes. In monkey hepatocarcinoma cells, intracellular total GSH decreased below 10% of the control value (approximately 25 micrograms/mg protein) when cells were grown for 44 h in medium deficient in cystine and methionine or in cystine alone. The latter finding indicated that transsulfuration from methionine to cysteine was defective in these neoplastic cells. In primary cultured adult rat hepatocytes, on the other hand, the transsulfuration pathway was intact, and total GSH decreased below 10% of control (approximately 20 micrograms/mg protein) only in cells grown in cystine- and methionine-deficient medium. In both cell types, the oxidized GSH fraction remained constant (2-5% of total). Incubation with 125I-labeled T4 and T3, followed by chromatography, was used to evaluate 5-deiodination in hepatocarcinoma cells and both 5- and 5'-deiodination in normal hepatocytes. Deiodination was not decreased by GSH deficiency in either case, but was actually increased in hepatocarcinoma cells. This resulted from an increase in the Vmax of 5-deiodinase related to growth arrest. Diamide at 2 mM reversibly inhibited both 5'- and 5'-deiodination in rat hepatocytes, accompanied by decreased total GSH as well as increased GSH disulfide (27% of total). The data suggest that GSH is so abundant in the liver that hepatocytes can tolerate a greater than 90% decrease in intracellular concentration without any change in thyroid hormone deiodination and indicate that altered thyroid hormone metabolism in the fetus and in starvation cannot be accounted for by a decreased hepatic GSH concentration.
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PMID:Glutathione deficiency induced by cystine and/or methionine deprivation does not affect thyroid hormone deiodination in cultured rat hepatocytes and monkey hepatocarcinoma cells. 679 Feb 65

The transport of L-alanine, L-serine, and L-cysteine has been studied in skin-derived diploid human fibroblasts in culture. Competition analysis, mathematical discrimination by nonlinear regression, and conditions varying the relative contribution of the various mediations have been used to characterize the systems engaged in the inward transport of these amino acids. All the adopted criteria yielded results showing that L-alanine, L-serine, and L-cysteine enter the cell by two Na+-dependent systems, System A and System ASC, and by a Na+-independent route, whose major component has been identified as System L. The apparent affinity of L-alanine, L-serine, and L-cysteine for the putative carrier was higher for System ASC than for System A. The transport Vmax for System A increased in response to cell starvation; after 12 h, its values were similar or higher than those exhibited by System ASC. At amino acid concentrations approaching those present in human plasma, System ASC appeared to be the primary mediation for the inward transport of L-alanine, L-serine, and L-cysteine in human fibroblasts. The contribution of System A was negligible in nonstarved cells and became appreciable under conditions of cell starvation. The Na+-independent System L made no substantial contribution to the uptake of L-alanine and L-serine and accounted for approximately one-fourth of the total uptake of L-cysteine.
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PMID:The transport of alanine, serine, and cysteine in cultured human fibroblasts. 680 40

Sulfate transport capacity was not regulated by cysteine, methionine, or glutathione in Pseudomonas halodurans, but growth on sulfate or thiosulfate suppressed transport. Subsequent sulfur starvation of cultures grown on all sulfur sources except glutathione stimulated uptake. Only methionine failed to regulate sulfate transport in Alteromonas luteo-violaceus, and sulfur starvation of all cultures enhanced transport capacity. During sulfur starvation of sulfate-grown cultures of both bacteria, the increase in transport capacity was mirrored by a decrease in the low-molecular-weight organic sulfur pool. Little metabolism of endogenous inorganic sulfate occurred. Cysteine was probably the major regulatory compound in A. luteo-violaceus, but an intermediate in sulfate reduction, between sulfate and cysteine, controlled sulfate transport in P. halodurans. Kinetic characteristics of sulfate transport in the marine bacteria were similar to those of previously reported nonmarine systems in spite of significant regulatory differences. Sulfate and thiosulfate uptake in P. halodurans responded identically to inhibitors, were coordinately regulated by growth on various sulfur compounds and sulfur starvation, and were mutually competitive inhibitors of transport, suggesting that they were transported by the same mechanism. The affinity of P. halodurans for thiosulfate was much greater than for sulfate.
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PMID:Assimilatory sulfur metabolism in marine microorganisms: characteristics and regulation of sulfate transport in Pseudomonas halodurans and Alteromonas luteo-violaceus. 726 10

In the rat hepatocyte, whether freshly separated or in primary culture, we do not find L-glutamine entry by Systems A and ASC as seen in cells previously studied. Instead the mediated entry of glutamine appears to occur exclusively by a Na+-dependent system ("N") apparently specific to amino acid amides and L-histidine; however, a portion of asparagine uptake occurs by System A. The simplest evidence for the separateness of the added system is the failure of model substrates for System A (e.g. N-methylalanine) to inhibit glutamine uptake significantly, and the failure of glutamine to inhibit the uptake of L-cysteine, model substrate for System ASC, at least in this cell. As is the case for cysteine, glutamine inhibits transport by System A (although not competitively), even though showing no transport by that system. Our finding confirms an earlier inference that glutamine uptake by this cell may follow a route not taken by alanine or serine, and explains the apparently erroneous companion inference that glutamine also shares a route with these two amino acids. Its uptake has now been characterized to show a series of differences from Systems A and ASC. Especially significant in view of the importance of glutamine metabolism are an insensitivity of the new system to stimulation by either insulin or glucagon, and its distinct enhancement (not as large as that for System A) on starvation of the cells with respect to amino acids. Hence, a second system has been found to show adaptive regulation.
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PMID:Characteristics of an amino acid transport system in rat liver for glutamine, asparagine, histidine, and closely related analogs. 737 63

Saccharomyces cerevisiae wine-producing yeast cultures grown under model winemaking conditions could be induced to liberate hydrogen sulfide (H2S) by starvation for assimilable nitrogen. The amount of H2S produced was dependent on the yeast strain, the sulfur precursor compound, the culture growth rate, and the activity of the sulfite reductase enzyme (EC 1.8.1.2) immediately before nitrogen depletion. Increased H2S formation relative to its utilization by metabolism was not a consequence of a de novo synthesis of sulfite reductase. The greatest amount of H2S was produced when nitrogen became depleted during the exponential phase of growth or during growth on amino acids capable of supporting short doubling times. Both sulfate and sulfite were able to act as substrates for the generation of H2S in the absence of assimilable nitrogen; however, sulfate reduction was tightly regulated, leading to limited H2S liberation, whereas sulfite reduction appeared to be uncontrolled. In addition to ammonium, most amino acids were able to suppress the liberation of excess H2S when added as sole sources of nitrogen, particularly for one of the strains studied. Cysteine was the most notable exception, inducing the liberation of H2S at levels exceeding that of the nitrogen-depleted control. Threonine and proline also proved to be poor substitutes for ammonium. These data suggest that any compound that can efficiently generate sulfide-binding nitrogenous precursors of organic sulfur compounds will prevent the liberation of excess H2S.
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PMID:Regulation of hydrogen sulfide liberation in wine-producing Saccharomyces cerevisiae strains by assimilable nitrogen. 757 81

Wheat germ lysate was used as a model system for in vitro translation. We show that an increase of the exchange surface between the reaction mixture and the atmosphere enhanced the amount of incorporated cysteine, indicating that early arrest of protein synthesis previously observed in such a system was due to oxygen starvation in the reaction mixture. This hypothesis was confirmed since the amount of proteins synthesized and the rate of translation increased when oxygen was added. We show that an addition of hydrogen peroxide to the translation mixture had the same effect as oxygen, allowing us to postulate that stimulation could be due to a common property between both molecules: the oxidizing behaviour. Free radicals in in vitro translation were believed to be involved since the utilization of iron chelating agents inhibited translation. This hypothesis was emphasized by the positive effect of a free radical generating system and the negative effect of free radical scavengers. These experiments suggest that the superoxide radical plays an important role in in vitro translation.
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PMID:Stimulation of translation by reactive oxygen species in a cell-free system. 764 10

The function and location of residue His-38 of the epsilon subunit of the Escherichia coli F1-ATPase were investigated. His-38 was replaced by glutamine and cysteine through site-directed mutagenesis to produce epsilon H38Q and epsilon H38C, respectively. Both epsilon H38Q and epsilon H38C fulfilled epsilon function in vivo as determined by growth on nonfermentable carbon sources, growth yield on limiting glucose, and recovery of cells from energy starvation conditions. epsilon H38Q and epsilon H38C were purified and studied in vitro. Pure epsilon H38C reacted rapidly with Ellman's reagent, indicating a surface location of the introduced cysteine. epsilon H38C which had been reconstituted with epsilon-depleted F1-ATPase could be linked specifically to the gamma subunit using two different heterobifunctional sulfhydril-reactive/photoreactive crosslinking agents, indicating that residue 38 lies near gamma. The mutated epsilon subunits were unaltered in their ability to inhibit epsilon-depleted F1-ATPase in vitro, even after modification of epsilon H38C with the bulky reagents fluorescein maleimide and N-(1-anilinonaphthyl-4)maleimide. It seems unlikely, therefore, that residue His-38 of epsilon interacts directly with gamma. Both the epsilon H38Q and epsilon H38C mutations reduced the recognition of epsilon by monoclonal antibody epsilon-1, but recognition of epsilon H38C was not further reduced by reaction with fluorescein maleimide. These results imply that residue 38 is not directly part of the epsilon-1 epitope, but plays a role in its formation.
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PMID:Location of conserved residue histidine-38 of the epsilon subunit of Escherichia coli ATP synthase. 768 92


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