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 5' region of the rRNA operon, rrnA, of M. capricolum was cloned. Sequence analysis revealed two tRNA genes, tRNA(leu) and tRNA(lys), upstream to the promoter of the rRNA operon. The in vivo transcription start sites of the rRNA operon and of the tRNA genes were mapped. The same promoters used by M. capricolum RNA polymerase are also recognized by E. coli RNA polymerase both in vivo and in vitro. We find that high levels of ppGpp in E. coli, resulting from amino acid starvation or from spoT mutation, activate rather than repress the transcription of the mycoplasma rrnA operon.
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PMID:Promoters of Mycoplasma capricolum ribosomal RNA operons: identical activities but different regulation in homologous and heterologous cells. 334 May 43

In Chinese hamster ovary cells, histidine starvation and inactivation of histidyl-tRNA synthetase by mutations or histidinol result in stimulation of protein breakdown. We have previously shown that the regulatory mechanism recognizes the level of aminoacylation of tRNA(His). We now report that it is also sensitive to the functional state of the ribosomes. Cycloheximide, an inhibitor of peptidyl-tRNA translocation, decreases the sensitivity of the regulation. In the presence of 1.5 micrograms cycloheximide/ml, protein synthesis is inhibited to 6% of control; a full response can still be elicited by appropriate concentrations of histidinol, but it requires a more extensive depletion of histidyl-tRNA than in the absence of cycloheximide. The response is attained only when the depletion is sufficient to inhibit protein synthesis further and to increase the number of ribosomes idling in the histidine codon with an empty aminoacyl site, measured by their reactivity in vivo to low concentrations of puromycin. The results indicate that a simple depletion of his-tRNA is not sufficient to elicit the response and suggest that idle ribosomes are required for regulation.
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PMID:Role of idle ribosomes in the response of Chinese hamster ovary cells to depletion of histidyl-tRNA. 339 91

Starvation for a single essential amino acid induced differentiation of the human promyelocytic leukemia line HL-60 into morphologically and functionally mature granulocytes. Differentiation occurred when protein synthesis was inhibited up to 90% but was not simply secondary to growth arrest or protein synthesis inhibition, because neither glucose starvation nor treatment with protein synthesis inhibitors induced differentiation. Induction of differentiation by an aminoacyl tRNA synthetase inhibitor and the effect of cycloheximide and puromycin on amino acid-starved cells suggested an important regulatory role of tRNA molecules during differentiation.
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PMID:Induction of HL-60 differentiation by starvation for a single essential amino acid but not by protein synthesis inhibitors. 346 16

Complexes of elongation factor Tu (EF-Tu) with guanosine 3'-diphosphate 5'-diphosphate (ppGpp) bind to ribosomes where they slow the incorporation of aminoacyl-tRNAs into protein by inhibiting both the binding of aminoacyl-tRNA.EF-Tu.GTP ternary complexes and the formation of peptide bonds. The latter action increases the time available for aminoacyl-tRNA rejection by the ribosome and, therefore, increases the effectiveness of proofreading. Synthesis of ppGpp and the formation of EF-Tu.ppGpp occur in vivo in response to amino acid starvation. Our finding, therefore, suggests an explanation for the otherwise puzzling observation that amino acid starvation has, at most, a moderate effect on the fidelity of protein synthesis in wild-type Escherichia coli. We suggest that an EF-Tu.ppGpp-induced increase in the effectiveness of proofreading buffers the overall translational fidelity of these cells against amino acid starvation-induced errors in initial selection of aminoacyl-tRNA ternary complexes.
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PMID:Elongation factor Tu.guanosine 3'-diphosphate 5'-diphosphate complex increases the fidelity of proofreading in protein biosynthesis: mechanism for reducing translational errors introduced by amino acid starvation. 351 44

We describe a simple method to quantitate the intracellular levels of charged tRNA species representing all 20 amino acids. Small RNA species are isolated from yeast cells under conditions where amino acids remain bound to their cognate tRNAs. After chromatographic removal of free amino acids, the tRNAs are discharged, and the amounts of the released amino acids are then quantitated. This method was applied to yeast cells from a wild type strain and from three mutant strains that are defective both in the general control of amino acid biosynthesis and in protein synthesis. Two of these mutant strains, previously shown to be defective in the methionine or isoleucine tRNA synthetases, respectively contain undetectable amounts of charged methionine or isoleucine although their levels of the remaining 19 amino acids are similar to a wild type strain. In contrast, a gcd1 mutant strain has normal levels of all 20 amino-acyl tRNA species. Thus, gcd1 strains are defective in general control of amino acid biosynthesis for reasons other than artifactual starvation of an amino acid due to a failure in tRNA changing.
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PMID:A rapid method for determining tRNA charging levels in vivo: analysis of yeast mutants defective in the general control of amino acid biosynthesis. 354 39

Yeast tRNA nucleotidyl transferase rapidly inactivates (half life c. 2 hr) upon nitrogen starvation of exponentially growing cells. The inactivation does not occur when glucose together with the nitrogen source is removed or when glucose is replaced by ethanol. The transferase activity reappears shortly after replenishment of the nitrogen source and this appearance of the enzymatic activity is blocked by cycloheximide, indicating the need for protein biosynthesis during the process. The nucleotidyl transferase activity is also very low in stationary phase yeast cells. A ten fold decrease in the transferase activity is not paralleled by loss of the integrity of the 3' end of the tRNA chains. It seems that there is a large excess of enzymatic activity over that needed to keep the tRNA chains complete. The observed lack of the 3' end of tRNAs from late stationary phase yeast cannot be accounted for by the observed drop in transferase activity in these cells.
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PMID:Inactivation of yeast nucleotidyl transferase and its effect on the integrity of the aminoacid acceptor end of transfer RNA. 355 80

The kinetics of the tRNA cycle is in itself capable of keeping the translational error level almost unaffected by amino acid starvation. There is no need to assume any yet unknown mechanism or property. Kinetic analysis shows that the concentration of aminoacyl-tRNA can stay high even for large reductions in aminoacylation, since the pool of uncharged tRNA normally is very small. An enhanced binding of uncharged tRNA to the ribosome could increase the effect and produce an extremely efficient error damping. A similar result is obtained when EF-Tu is partially inhibited by ppGpp.
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PMID:Maintenance of accuracy during amino acid starvation. 366 30

In Salmonella typhimurium, expression of the leucine operon is regulated by a transcription attenuation mechanism. According to a current model of attenuation, elevated expression of this operon requires that a ribosome stall at one of four adjacent codons for leucine on a leader RNA. We used oligonucleotide-directed mutagenesis to convert the four leucine codons of the S. typhimurium leu leader to four threonine codons. Analysis of the resulting mutant operon showed that almost all regulation by leucine had been abolished. The mutant operon was, instead, partially derepressed by a limitation for charged threonine tRNA. These results provide direct evidence for the function for the four leucine codons postulated by the attenuator model. An unexpected observation made during these studies was that the wild-type leu operon was partially derepressed by starvation for threonine.
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PMID:Mutations that convert the four leucine codons of the Salmonella typhimurium leu leader to four threonine codons. 392 57

l-Threonine deaminase (l-threonine dehydratase [deaminating], EC 4.2.2.16) has been shown to be involved in the regulation of three of the enzymes of isoleucine-valine biosynthesis in yeast. Mutations affecting the affinity of the enzyme for isoleucine also affected the repression of acetohydroxyacid synthase, dihydroxyacid dehydrase, and reductoisomerase. The data indicate that isoleucine must be bound for effective repression of these enzymes to take place. In a strain with a nonsense mutation midway in liv 1, the gene for threonine deaminase, starvation for isoleucine or valine did not lead to derepression of the three enzymes; starvation for leucine did. The effect of the nonsense mutation is recessive; it is tentatively concluded, therefore, that intact threonine deaminase is required for derepression by two of the effectors for multivalent repression, but not by the third. A model is presented which proposes that a regulatory species of leu tRNA(leu) is the key intermediate for repression and that threonine deaminase is a positive element, regulating the available pool of charged leu tRNA by binding it.
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PMID:Involvement of threonine deaminase in repression of the isoleucine-valine and leucine pathways in Saccharomyces cerevisiae. 457 Jul 83

Changes in the cell content and rate of synthesis of mRNA were studied in auxotrophs of Escherichia coli recovering from a period of amino acid deprivation. Parallel studies were carried out on bacterial strains inhibited with trimethoprim, when glycine and methionine were added to relieve an amino acid deficiency. In the latter case, protein synthesis was still severely inhibited through a lack of N-formylmethionyl-tRNA(fMet) for chain initiation, so that fewer ribosomes were attached to mRNA chains. (1) In RC(str) strains recovering from amino acid starvation, there was a transient oversynthesis of mRNA, but the amounts returned to normal after about a 15-min period of recovery. RC(rel) strains did not show this effect; any extra mRNA accumulated during the previous starvation period was rapidly lost, but no oversynthesis occurred during the resumption of growth. (2) In trimethoprim-inhibited cultures supplemented with glycine and methionine, mRNA was produced at the same rate, relative to stable RNA species, as during normal growth. The evidence implied that decreased rates of ribosome attachment had no effect on the functional or chemical lifetime of the mRNA fraction. This suggests that mRNA stability does not depend on the frequency of translation by ribosomes. (3) Changes in the mRNA contents of trimethoprim-inhibited RC(str) and RC(rel) cultures were noted soon after supplementation with glycine and methionine. These closely followed those observed in cultures recovering from simple amino acid withdrawal.
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PMID:The control of ribonucleic acid synthesis in bacteria. Fluctuations in messenger ribonucleic acid synthesis in cultures recovering from amino acid starvation. 459 30


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