Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Certain developmental mutants of Myxococcus xanthus can be complemented (extracellularly) by wild-type cells. Insertions of Tn5 lac (a transposon which couples beta-galactosidase expression to exogenous promoters) into developmentally regulated genes were used to investigate extracellular complementation of the A group mutations. A- mutations reduced developmental beta-galactosidase expression from 18 of 21 Tn5 lac insertions tested and that expression was restored to A- Tn5 lac cells by adding wild-type cells. The earliest A-dependent Tn5 lac normally expresses beta-galactosidase at 1.5 hr of development indicating a developmental block at 1-2 hr in A- mutants. A substance which can rescue the expression of this early Tn5 lac is released by wild-type (A+) but not by A- cells. This substance appears in a cell-free wash of wild-type cells or in starvation buffer conditioned by wild-type cells 1-2 hr after development is initiated. The conditioned starvation buffer also restores normal morphological development to an A- mutant.
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PMID:Intercellular signaling is required for developmental gene expression in Myxococcus xanthus. 301 95

Studies were made of the synthesis of Lac messenger ribonucleic acid (mRNA) by Escherichia coli in the absence of protein synthesis and of the coupling of transcription of lac operon to translation. Lac mRNA was not synthesized in the presence of chloramphenicol, and its synthesis steadily decreased during K(+) deprivation and treatment with puromycin. Since under these conditions total mRNA synthesis is not inhibited it is suggested that the control of Lac mRNA is distinct from that which regulates total mRNA synthesis. Lac mRNA synthesized during recovery from K(+) starvation or from chloramphenicol inhibition is not translated into functional enzyme, suggesting translational control over beta-galactosidase synthesis.
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PMID:Dissociation of Lac messenger ribonucleic acid transcription from translation during recovery from inhibition of protein synthesis. 455 40

Pyridoxineless mutants of Escherichia coli B stopped incorporation of nucleosides into trichloroacetic acid-insoluble material about 40 to 60 min after pyridoxine starvation was initiated, whereas incorporation of amino acids (measured the same way) slowed but did not stop for several hours. Both these incorporations and cell density were increased most effectively by the presence of either threonine or isoleucine. Arginine, glutamate, histidine, methionine, tryptophan, and tyrosine also caused significant but less dramatic increases. Inducibility of beta-galactosidase continued beyond the point where nucleic acids appeared to stop their synthesis, suggesting that messenger ribonucleic acid synthesis continued beyond ribosomal ribonucleic acid synthesis. This inducibility was also increased by isoleucine and threonine. The overall results suggest that the threonine-isoleucine biosynthetic pathway is the most sensitive to starvation for pyridoxine.
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PMID:Isoleucine and threonine can prolong protein and ribonucleic acid synthesis in pyridoxine-starved mutants of Escherichia coli B. 456 72

The rates of elongation of beta-galactosidase and its messenger ribonucleic acid (RNA) were estimated in a polyamine-deficient mutant of Escherichia coli through an analysis of the kinetics of enzyme induction. The chain growth of beta-galactosidase was calculated from the time required after the appearance of an amino terminal fragment of 60 amino acids (auto-alpha) until completed enzyme began to accumulate. The elongation rate of beta-galactosidase messenger RNA was estimated from the time after induction at which streptolydigen-resistant, enzyme-forming capacity first appeared. Upon polyamine starvation, the rate of polypeptide elongation slowed from 17 to 10 amino acids per s and the messenger RNA elongation rate decreased from 47 to 30 nucleotides per s. These reductions in polymerization rates were proportional to the decrease in cellular growth rate produced by polyamine starvation. It was concluded that, although it is quite unlikely that polyamine levels are involved in regulation of cell growth, they may be acting as cofactors in the synthesis of RNA or protein, or both.
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PMID:Influence of polyamine limitation on the chain growth rates of beta-galactosidase and of its messenger ribonucleic acid. 458 42

The concentration of rifampin necessary to affect the initiation of ribonucleic acid (RNA) synthesis quickly in Escherichia coli strains K-12 and 15TAU was about 200 mug/ml, as determined by extrapolation of the effect of the drug on the induction of beta-galactosidase synthesis. A lag in the action of rifampin of about 10 s was confirmed. Rifampin was then used as a probe to compare RNA synthesis in growing and amino acid-starved E. coli. Restoring arginine to arginine-starved strain 15TAU immediately after rifampin inhibition did not detectably restore the rate of uracil uptake to that of uninhibited cells. The residual rate of RNA synthesis (corrected for acid-soluble triphosphate specific activities) after rifampin treatment of both growing and isoleucine-starved (valine-inhibited) cultures of strain K-12 showed similar decay kinetics. These findings support the notion that amino acid starvation blocks the initiation of some RNA transcription units, but do not rule out other possibilities.
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PMID:Decay of ribonucleic acid synthesis in amino acid-starved Escherichia coli after rifampin treatment. 459 64

The rate of polypeptide chain elongation during steady-state, polyamine-limited growth of a mutant of Escherichia coli was measured by two independent techniques. Analysis of polysome patterns gave values of 17.5 and 9.5 amino acids per s at 37 C in unstarved and polyamine-limited cells, respectively. From the kinetics of entry of labeled amino acids into polypeptides of defined molecular weights, values at 30 C of 10.1 and 5.8 amino acids per s were obtained for unstarved and polyamine-limited cultures, respectively. Correction of these values to 37 C resulted in rates of 15.0 and 8.7 amino acids per s. These results support the previous conclusion, based on the kinetics of beta-galactosidase induction, that polyamine starvation decreases the rate of protein synthesis by limiting the velocity of polypeptide chain elongation.
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PMID:Polyamine limitation of growth slows the rate of polypeptide chain elongation in Escherichia coli. 460 21

In order to relate the biogenesis of the lactose transport system to lipid synthesis, a glycerol-requiring mutant of Escherichia coli K-12 with a specific defect in l-glycerol-3-phosphate synthesis was isolated and characterized. The defective enzyme is the biosynthetic l-glycerol-3-phosphate dehydrogenase [l-glycerol-3-phosphate: NAD (P) oxidoreductase, EC 1.1.1.8] which functions as a dihydroxyacetone phosphate reductase to provide l-glycerol-3-phosphate for lipid synthesis. In this mutant, removal of glycerol from the growth medium results in inhibition of the synthesis of protein, deoxyribonucleic acid, and phospholipid. Inhibition of phospholipid synthesis immediately follows glycerol removal, whereas the inhibition of deoxyribonucleic acid and protein synthesis is preceded by a short lag period. Glycerol starvation does not change the turnover pattern of previously synthesized phospholipids. The blocking of lipid synthesis by glycerol starvation causes a drastic decrease in inducibility of beta-galactoside transport activity relative to beta-galactosidase, indicating that induction of lactose transport requires de novo lipid synthesis.
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PMID:Induction of the lactose transport system in a lipid-synthesis-defective mutant of Escherichia coli. 491 67

1. Experiments with rifampicin and stringent strains of Escherichia coli (pro(-)purB(-)rel(+)) indicate that purine deficiency does not decrease and may considerably increase the potential for RNA synthesis by RNA polymerase molecules that are bound to DNA and have already commenced transcription. 2. DNA-RNA hybridization experiments indicate that purine starvation increases the distribution of bound RNA polymerase molecules between the cistrons for mRNA and those for stable RNA. 3. Synthesis of beta-galactosidase mRNA is more dependent on the ability to synthesize guanine nucleotides than on the ability to synthesize adenine nucleotides. 4. Amino acid starvation tends to decrease the potential for RNA synthesis by RNA polymerase molecules bound to DNA. 5. Since this effect differs from that due to purine starvation, amino acid control of RNA synthesis does not appear to operate solely by causing a deficiency of purine nucleotides. 6. The results are discussed in terms of the ability to initiate RNA chains and to extend them under different circumstances.
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PMID:Synthesis of ribonucleic acid in purine-deficient Escherichia coli and a comparison with the effects of amino acid starvation. 492 43

Inducible and constitutive beta-galactosidase formation and radioactive amino acid incorporation were measured in cells recovering from various treatments which inhibit protein synthesis in the cell. Undelayed beta-galactosidase formation was found in stringent auxotrophs recovering from amino acid starvation, in cells recovering from glycerol or potassium starvation, and in bacteria recovering from puromycin treatment. Delayed beta-galactosidase formation was found in relaxed auxotrophs recovering from amino acid starvation and in prototrophs recovering from chloramphenicol or from tetracycline treatment. The length of this delay was directly proportional to the duration of the treatment. All cells recovering from the various treatments exhibited a slightly decreased rate of beta-galactosidase formation and an increase in radioactive amino acid incorporation.
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PMID:Inducible and constitutive -galactosidase formation in cells recovering from protein synthesis inhibition. 494 86

Paigen, Kenneth (Roswell Park Memorial Institute, Buffalo, N.Y.). Phenomenon of transient repression in Escherichia coli. J. Bacteriol. 91:1201-1209. 1966.-A family of mutants has been obtained in Escherichia coli K-12 in which beta-galactosidase is not inducible for approximately one cell generation after the cells are transferred to glucose from other carbon sources. After that period; the enzyme can be induced at the level appropriate to glucose-grown cultures of the parent cells. Among a wide variety of carbon sources, the only one capable of eliciting a state of transient repression is glucose. Conversely, transient repression occurs when cells are transferred to glucose from any of a variety of other carbon sources. The only exceptions to this so far discovered are lactose, gluconate, and xylose. Susceptibility to transient repression in mutants can also be induced in glucose-grown cells by a period of starvation. Mutant cells which have become susceptible to transient repression lose susceptibility in the presence of glucose only when they are under conditions which permit active protein synthesis. The presence of an inducer of beta-galactosidase is not required during this time, nor does pre-induction for beta-galactosidase diminish the susceptibility of mutants. At least two other catabolite repression-sensitive enzymes (galactokinase and tryptophanase) are also sensitive to transient repression, and the two phenomena are probably related. The absolute specificity of glucose and the pattern of response seen after growth in different carbon sources suggest that the endogenous metabolite which produces these repressions is far more readily derived from glucose in metabolism than it is from any other exogenous carbon source.
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PMID:Phenomenon of transient repression in Escherichia coli. 532 97


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