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)

The mode of induction of beta-galactosidase (EC 3.2.1.23) in synchronously growing cultures of two Hfr strains of Escherichia coli K12 was investigated. Cells can be induced to form the enzyme during any portion of the cell cycle; but when they are grown permanently in the presence of an inducer, enzyme synthesis is discontinuous. The interruption of beta-galactosidase synthesis appears to be geared to the growth cycle: it occurs when the cells are dividing actively. The observation that lac-specific messenger RNA is produced also in the absence of detectable enzyme synthesis suggests the existence of a control mechanism operating on the level of translation.
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PMID:On the control of the induction of -galactosidase in synchronous cultures of Escherichia coli. 494 12

An operon fusion of the lac genes to those required for synthesis of type 1 fimbriae (pili) has been achieved in a K12 strain of Escherichia coli lysogenized by the bacteriophage mu d (Ap4, lac). Synthesis of beta-galactosidase, therefore, reflected pil gene transcription and was used as a probe of fimbrial regulation. Expression of the operon fusion was found to oscillate, demonstrating that phase variation between fimbriate and nonfimbriate states is under transcriptional control. The transition rates from fimbriate to nonfimbriate were 1.05 X 10(-3) per bacterium per generation and from nonfimbriate to fimbriate, 3.12 X 10(-3) per bacterium per generation.
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PMID:Phase variation of type 1 fimbriae in Escherichia coli is under transcriptional control. 611 79

Although no beta-galactosidase activity could be induced in Escherichia coli K12 during uridine starvation, material which cross-reacted with antiserum against beta-galactosidase could be detected. The synthesis of enzymically inactive proteins during uridine starvation appeared to be due to errors in transcription.
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PMID:Mis-transcription during uridine starvation in Escherichia coli K12. 615 19

The SOS-function-inducing activities of 42 chemical mutagens were investigated in Escherichia coli K12. The induction of the SOS function was assayed by monitoring the beta-galactosidase activity in the sulA::lacZ fusion strain PQ37 . To correct for the inhibitory effects of test chemicals on mRNA or protein synthesis, the level of the constitutive alkaline phosphatase was assayed in parallel. Most of the mutagens reported to be mutagenic to the Ames' Salmonella tester strains showed the SOS-function-inducing activity. The inducible SOS repair may be responsible for not only base-change mutations but also frameshift mutations. However, 9-aminoacridine, ethidium bromide and 4-nitro-o-phenylenediamine did not induce the SOS function, suggesting that the mutagenesis induced by these mutagens may occur independently of SOS repair. Present results support the SOS mutagenesis model that error-prone SOS repair plays an important role in mutagenesis induced by most chemical mutagens.
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PMID:The SOS-function-inducing activity of chemical mutagens in Escherichia coli. 620 35

5-Azacytidine inhibits Escherichia coli DNA(cytosine-5)methylase when added to growing cells. The time-course of recovery of methylase activity and the appearance of 5-methylcytosine in DNA following removal of the drug was studied. When E. coli K12 was treated with 5-azacytidine for 30 min, DNA (cytosine-5)methylase levels decreased to less than 10% of control levels and slowly recovered to control levels after seven generations of growth. 5-Methylcytosine synthesis in DNA remained at less than 10% of control levels for three generations after treatment and returned to control levels after six generations of growth. In contrast, beta-galactosidase levels in induced cells, which declined to 66% of control one generation after treatment, returned to control by the third generation of growth. The rate of induction of beta-galactosidase had returned to the control rate two generations after growth resumed. Since azacytidine-containing DNA inhibits DNA-cytosine methylases in vitro, the prolonged inhibition of cytosine methylation in E. coli K12 following treatment with the drug could be due to the persistence of the drug in DNA and thus inhibition of newly synthesized enzymes.
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PMID:Effect of 5-azacytidine on deoxyribonucleic acid methylation in Escherichia coli K12. 620 59

The control of beta-galactosidase specified by the lactose transposon Tn951 (inserted into RP1 to give pGC9114) has been studied in Escherichia coli K12, Proteus mirabilis, Pseudomonas aeruginosa and Pseudomonas putida; in the first two species comparison could be made with Flac. In E. coli K12, the Tn951 and chromosomally encoded enzymes showed marked qualitative differences in regulatio, the former giving a substantially lower maximum induced level and induction ratio. Several parameters were slightly affected by strain background. In P. mirabilis, beta-galactosidase control determined by both Flac (in accord with earlier work) and pGC9114 was markedly different from E. coli in that maximal induced levels were about an order of magnitude lower and the induction ratio was reduced to 3 to 5. In Ps. aeruginosa and Ps. putida, Tn951-specified lac expression was qualitatively similar to that in P. mirabilis. Possible reasons for anomalous expression in Proteus and Pseudomonas are discussed.
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PMID:Expression of the lactose transposon Tn951 in Escherichia coli, Proteus and Pseudomonas. 625 Nov 61

Escherichia coli K12 growing anaerobically on L-fucose excretes L-1,2-propanediol as a fermentation product whose formation is catalysed by an inducible NAD-linked oxidoreductase. The activity of this enzyme is highly induced only during anaerobic growth. Three bacterial strains bearing a hybrid operon with the structural genes for lactose utilization (lacZYA) fused to the promoter of the propanediol oxidoreductase gene (fucO) were constructed to test whether or not transcriptional control was involved. In contrast to propanediol oxidoreductase of wild-type cells, beta-galactosidase in the phi(fuc-lac) strains was induced by fucose to high levels both aerobically and anaerobically. Data from this work are in accord with the previous report that the enzyme protein (assayed by specific antibodies) was induced both aerobically and anaerobically, but that only in anaerobically grown cells was the oxidoreductase catalytically active. In the present study, we found that the oxidoreductase induced anaerobically in wild-type cells remained enzymically active during aerobic growth in the absence of fucose. On the other hand, wild-type cells grown aerobically in the presence of fucose and then allowed limited anaerobic growth on glucose did not gain any oxidoreductase activity. The mechanism of this post-transcriptional control remains to be discovered.
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PMID:Use of operon fusions to examine the regulation of the L-1,2-propanediol oxidoreductase gene of the fucose system in Escherichia coli K12. 631 47

2-ketobutyrate and its analogues were found to inhibit strongly and transiently the rate of beta-galactosidase synthesis in Escherichia coli K12. This effect was ascribed to a strong and transient inhibition of the adenylate cyclase activity. By using pts mutants, we showed, in agreement with our previous results (Daniel et al. 1983), that the likely target of 2-ketobutyrate and its analogues is the phosphoenolpyruvate: glycose phosphotransferase transport system (PTS). Furthermore, evidence for such a cascade effect caused by 2-ketobutyrate and its analogues allowed us to corroborate our previous proposal (Daniel et al. 1983) that 2-ketobutyrate, a precursor of isoleucine, acts as an E. coli alarmone monitoring the passage from anaerobic to aerobic growth conditions.
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PMID:Role of 2-ketobutyrate as an alarmone in E. coli K12: inhibition of adenylate cyclase activity mediated by the phosphoenolpyruvate: glycose phosphotransferase transport system. 632 19

Mutations in the xylose-H+ transport activity of Escherichia coli K12 were isolated using Mud(ApRlac). The initial selection was for simultaneous acquisition of ampicillin and xylose resistance in an fda background. Colonies were then screened for xylose-inducible beta-galactosidase and for growth on xylose of their fda+ derivatives. Two of the xylose-positive derivatives were shown to be impaired in xylose-H+ symport in whole cells and in xylose transport into subcellular vesicles. Their xylose transport in whole cells showed increased sensitivity to arsenate. The site of prophage insertion was mapped to 91.4 min on the E. coli genome between pgi and malB. It is proposed that the gene for the xylose-H+ symport system be called xylE.
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PMID:Location of a structural gene for xylose-H+ symport at 91 min on the linkage map of Escherichia coli K12. 636 12

Bisulfite reversibly inhibits the growth of a variety of microorganisms and has been used as a preservative in foods and beverages for that reason. We have now measured macromolecule synthesis in Escherichia coli K12 after bisulfite treatment. RNA synthesis, the synthesis of total protein, and of an inducible enzyme, beta-galactosidase, stopped almost immediately upon addition of 2 mM (or higher concentrations) of bisulfite. These functions resumed after a lag whose duration depended on the concentration of bisulfite added. The synthesis of DNA was slowed upon bisulfite addition, but did not stop entirely. The inhibition of RNA synthesis by bisulfite took place in both stringent and relaxed strains of E. coli and was not relieved upon addition of chloramphenicol. Stringent control was therefore not involved in this effect. No effect on protein synthesis was observed in the cell-free system of E. coli (using poly(U) or MS2 RNA as messenger) at bisulfite concentrations up to 10 mM. Protein synthesis inhibition in vivo was apparently not due to a reaction of bisulfite with a component of this system. In additional experiments, RNA polymerase was not impaired by bisulfite, and the growth inhibition effect was shown to proceed in the presence of inhibitors of free radical chain reactions.
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PMID:The effects of bisulfite on growth and macromolecular synthesis in Escherichia coli. 640 16


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