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)

Upon addition of excess one carbon metabolites (including serine)bacteria stop growing because of isoleucine starvation. After such treatment stringent bacteria rapidly resume normal growth whereas relaxed mutants remain unable for some time to grow. We show here that this is due to a lack of derepressibility of ilv genes after the starvation period. Results are also presented which show that RNA polymerase structural mutants may be selected among the clones resistant to a mixture of serine, methionine and glycine, in relA- strains. Finally circumstancial evidence suggests that the one carbon metabolism may be involved in a process controlling isoleucine metabolism.
Mol Gen Genet 1978 Sep 20
PMID:Correlation between the serine sensitivity and the derepressibility of the ilv genes in Escherichia coli relA- mutants. 36 63

Ferrichrome-promoted iron uptake in Escherichia coli K12 is strictly dependent upon the tonA gene product, a 'minor' outer membrane protein. By selection for mutants of E. coli resistant to phages which require 'major' outer membrane proteins as receptors, strains with pronounced protein deficiencies were constructed. Such strains were tested for anomalous behaviour of ferrichrome transport. No significant differences in iron uptake were detected in E. coli K12 strains with markedly reduced amounts of protein I. However, a reduction in the initial velocity (up to 40%) was observed in E. coli deficient in outer membrane protein II. This difference was only evident when cells were grown under iron-starvation conditions; it was abolished when cells were grown in rich medium. Kinetic parameters for ferrichrome transport were determined for maximum velocity but for Km; double reciprocal plots showed a biphasic nature, probably attributable to a limited number of outer membrane binding sites and to the multi-component nature of the ferrichrome-iron transport system.
J Gen Microbiol 1979 Jan
PMID:Protein II influences ferrichrome-iron transport in Escherichia coli K12. 37 90

A new class of mutants of E. coli exhibiting altered metabolism of ppGpp and pppGpp has been isolated, and mapped at a locus designated gpp, near min 83 on the genetic map. These mutants accumulate elevated levels of pppGpp during amino acid starvation or carbon source downshift, and exhibit a reduced rate of pppGpp degradation in vivo. The in vitro evidence suggests that the gpp mutants are defective in a 5'-nucleotidase, which specifically hydrolyzes pppGpp to ppGpp. Certain combinations of gpp and spoT mutations are inviable. A gpp spoT double mutant, constructed by employing a leaky spoT mutation, was found to have a slower rate of pppGpp degradation than the gpp mutant alone. This result indicates that spoT also participates in pppGpp degradation. The inviability of certain gpp spoT combinations is attributed to the inability of the double mutants to degrade pppGpp. This is supported by the observation that selection for increased growth rate on the double mutant results in the recovery of relA mutations. Various effects of the gpp mutation upon the pppGpp and ppGpp pools provide additional support for a scheme in which pppGpp is the major precursor of ppGpp.
Mol Gen Genet 1979 Feb 01
PMID:Mutants of Escherichia coli defective in the degradation of guanosine 5'-triphosphate, 3'-diphosphate (pppGpp). 37 53

The ultrastructure of the wall of Candida albicans strain 6406 was examined in polyeneresistant organisms obtained by continued incubation after the cessation of growth. The walls of organisms harvested either during the exponential phase of growth or after 24 h starvation, when examined in situ, showed the typical layered appearance. After 72 h starvation, when the resistance to amphotericin B methyl ester (AME) was 60 times greater than that of exponentially growing organisms, both the periplasmic material and the distinct electron-dense layers were absent from the wall. At this stage there was no increase in the thickness of the wall. After 144 h starvation the thickness of the wall had increased from 143 +/-22 nm (exponential phase organisms) to 211+/-58 nm. If after 144 h starvation the organisms were incubated for 1 h in fresh nutrient medium they regained their sensitivity to AME and the wall regained the periplasmic material and its characteristic multilayered appearance. During the first 24 h starvation there was a considerable fall in the soluble glucan fraction, but on continued incubation there was little change in the relative proportions of the major carbohydrate constituents of the cell. Thin sections of purified walls isolated from organisms harvested either during exponential growth or after 144 h starvation were identical in appearance and characterized by the absence of the electrondense layers observed in sections of intact cells and by a reduction in thickness to 100+/-20nm.
J Gen Microbiol 1979 Feb
PMID:Ultrastructural changes in the cell wall of Candida albicans following cessation of growth and their possible relationship to the development of polyene resistance. 37 81

The restriction nuclease cleavage pattern of E. coli DNA synthesized in vitro in the cellophane membrane system (Schaller et al., 1972) is similar to the one obtained after labelling E. coli in vivo. This is shown for exponentially growing cells and for cells synchronized by amino acid starvation followed by thymine starvation. In synchronized cells a piece of some 180 kilobase pairs is labelled containing oriC and neighbouring regions at 82 min on the genetic map of E. coli. A pulse label in vitro is incorporated into the same piece of DNA, but the center of this region, i.e. the EcoR1 fragment of 8.6 kbp length which contains the oriC region (Marsh and Worcel, 1977; v. Meyenburg et al., 1977; Yasuda and Hirota, 1977) is missing.
Mol Gen Genet 1979 Jan 16
PMID:In vitro replication of a DNA fragment containing the vicinity of the origin of E. coli DNA replication. 37 97

It has been shown that in bacteria, besides specific regulatory mechanisms, the synthesis of aminoacid biosynthetic enzymes is also controlled by the endogenous aminoacid pool. The latter regulates the intracellular level of ppGpp, a positive effector of RNA messenger transcription. A similar regulatory control exists in yeast but does not appear to involve the same general effector. This was established by the observation that derepression of the enzymes belonging to several aminoacid biosynthetic pathways follows aminoacid starvation or tRNA discharging. We now report the repression of the arginine pathway by the total aminoacid pool. New mutations affecting the repressibility of the arginine enzymes as well as enzymes belonging to other aminoacid biosyntheses, when cells are grown in the presence of an excess of aminoacids, were identified.
Mol Gen Genet 1979 Jan 16
PMID:Concerted repression of the synthesis of the arginine biosynthetic enzymes by aminoacids: a comparison between the regulatory mechanisms controlling aminoacid biosyntheses in bacteria and in yeast. 37 2

A study has been made of the regulation of the synthesis of Pl double-stranded (ds) RNA, the genome of the yeast virus-like particle. When yeast protein synthesis is prevented by starvation for a required amino acid or by addition of cycloheximide, the rate of Pl dsRNA synthesis is reduced markedly. During nitrogen starvation the synthesis of Pl dsRNA persists but is accompanied by the degradation of pre-existing molecules. This degradation appears to require the induction of new enzymes and it is likely that the breakdown products are used to enable the cell to complete its division cycle. However, all of the copies of the VLP genome are not degraded in this process, some are conserved and can replenish the amount of Pl dsRNA on return to growth conditions. The controls which must operate on Pl dsRNA synthesis are discussed and compared with those exerted on nuclear RNA synthesis in yeast.
Mol Gen Genet 1979 Mar 20
PMID:The regulation of RNA synthesis in yeast IV. Synthesis of double-stranded RNA. 37 28

The plasmid pMY3, which was constructed so as to express the Su+7 amber suppressor tRNA gene, also relaxes control of stable RNA synthesis in stringent cells. The relaxation is not growth medium or strain-dependent and does not occur in the presence of the vehicle alone. When expression of the effective sequence is diminished, in a lysogen of phi 80d3 ilv+Su+7, the sequence no longer affects RNA synthesis. The relaxation is general, extending to all or almost all tRNA loci, including tRNAs located in the ribosomal spacer regions, and to all ribosomal RNAs. Relaxed plasmid-carrying strains are still able to elevate guanosine tetra- and penta-phosphate levels in response to amino acid starvation, but steady state levels are somewhat diminished. Aminoacyl-tRNA falls to control levels when the plasmid-carrying strain is deprived of amino acid. Therefore, the relaxed strain perceives amino acid starvation, but does not respond normally. These properties define a novel locus which relaxes stringent control.
Mol Gen Genet 1979 Mar 05
PMID:Relaxation of stable RNA synthesis by a plasmid-borne locus. 37 46

Studies were undertaken to determine if mitochondrial rRNA synthesis in yeast is regulated by general cellular stringent control mechanism. Those variables affecting the relaxation of a cycloheximide-induced stringent response as a result of medium-shift-down or tyrosine limitation include: 1) the stage of cell growth, 2) carbon source, 3) strain differences and, 4) integrity of the cell wall. The extent of phenotypic relaxation decreased or was eliminated entirely in a strain dependent manner as cells entered stationary phase of growth or by growth of cells on galactose or in osmotically stabilized spheroplast cultures. Cytoplasmic and mitochondrial RNA species were extracted from regrowing spheroplast cultures subjected to different experimental regimens and analyzed by electrophoresis on 2.5% polyacrylamide gels. Relative rates of synthesis were determined in pulse experiments and normalized by double-label procedures to longterm label material. Tyrosine starvation was found to inhibit synthesis of the large and small rRNA species of both cytoplasmic and mitochondrial rRNAs to about 5-20% of the control values. Chloramphenicol inhibits mitochondrial and cytoplasmic rRNA synthesis to 60-80% of control; however, chloramphenicol addition does not relax the stringent inhibition of either class of rRNAs. Cycloheximide addition results in 70-80% inhibition of synthesis of both cellular speceis of rRNAs. As noted above, cycloheximide does not relax the stringent response of cytoplasmic rRNA synthesis in spheroplasts, and also does not relax the stringent inhibition of mitochondrial rRNA synthesis. From these studies, we conclude that both cytoplasmic and mitochondrial rRNA synthesis share common control mechanisms related to regulation of protein synthesis by shift-down or amino acid limitation.
Mol Gen Genet 1979 Jun 20
PMID:Regulation of mitochondrial ribosomal RNA synthesis in yeast. I. In search of a relaxation of stringency. 38 47

Inactivation of the dna B or dna D gene product in Bacillus subtilis stimulates RNA and protein synthesis. Strains containing ts dna B and D mutations have been constructed by introducing the mutations by transformation into a thymine requiring strain which does not lyse during thymine starvation. The consequences of inactivation of these gene products have been assessed by comparing RNA and protein synthesis during thymine starvation at the restrictive temperature with the recipient strain. In the ts+ strain, there is a doubling in rate of RNA synthesis during thymine starvation. In the ts dna B and D mutations at the restrictive temperature the rate of RNA synthesis increases four fold. By preincubating the mutants in the absence of thymine for one generation at the permissive temperature the two fold increase in rate of RNA synthesis associated with inactivation of the initiation complex can be demonstrated under conditions where the ts+ strain shows a decrease in rate of RNA synthesis. The rate of protein synthesis observed largely reflects the rate of RNA synthesis in all strains. Completion of the chromosome at the restrictive temperature has no significant effect on the rate of RNA synthesis. It is suggested that inactivation of the initiation complex after chromosome initiation could play an important role in control of RNA synthesis in relation to the cell cycle.
Mol Gen Genet 1977 Oct 24
PMID:Macromolecular synthesis in chromosome initiation mutants of Bacillus subtilis. 41 65


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