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)

A recombinant Myxococcus xanthus strain was constructed that constitutively produces two proteins from Escherichia coli, the cytoplasmic beta-galactosidase and the periplasmic pH 2.5 acid phosphatase (AppA protein). We have previously shown that during vegetative growth, AppA protein is partly accumulated in the periplasm of M. xanthus and partly released into the medium. We demonstrate here that during starvation-induced development, release of periplasmic AppA protein to the medium did not occur over a period of 20 h. This was coincident with, but not caused by, the arrest of the synthesis of the foreign proteins. We have shown that this lack of secretion could be attributed to starvation per se and did not depend on the ability of the cells to undergo development. Our findings suggest that protein secretion which occurs during the first hours of starvation-induced development might therefore take place via a different route from that which occurs in vegetative cells.
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PMID:Starvation yields a drastic decrease in outer-membrane permeability to a periplasmic foreign protein in Myxococcus xanthus. 857 5

Dictyostelium discoideum is a simple eukaryote that lives as an amoeba until starvation triggers aggregation. The aggregate forms a slug which then develops into a fruiting body with two main cell types, stalk and spore cells. Two mechanisms have been proposed to explain cell-type differentiation. Studies using expression of the ecmA gene as a prestalk cell marker indicated that gradients of morphogens determine cell fate in the slug. However, studies using dyes or the cysteine proteinase 2 (CP2) gene product as a prestalk cell marker indicated that cell autonomous factors such as cell-cycle phase at the time of starvation cause an initial choice of cell fate. To help resolve these differences, we have used transformed cells containing the promoter of the prestalk gene ecmA fused to beta-galactosidase (Jermyn and Williams, 1991) to study the differentiation of Dictyostelium cells at low cell density, at which cell-to-cell interactions and morphogen gradients are minimal. We find that under all conditions of low cell density in which express ion the ecmA fusion gene occurs, it is invariably detected in less than 25% of the cells from a clonal population. This suggests that a cell-autonomous mechanism is involved in ecmA expression. We then used double-labeled immunofluorescence to examine the ontogeny of the CP2-positive and the ecmA-positive cells. In developing aggregates, 9 to 12% of the cells are CP2-positive from 12 to 24 hr of development. The ecmA-positive cells are first detected at 16 hr as a subset of the CP2-positive cells and then increase in number. At approximately 20 hr, the CP2-positive cells and the ecmA-positive cells are almost completely overlapping sets. By late development, all of the CP2-positive cells are ecmA-positive and an additional 10% of the CP2-negative cells are also ecmA-positive. This indicates that up to 20 hr development, ecmA is expressed only in CP2-positive cells. The data thus suggest that cell-cycle phase at the time of starvation causes an initial choice of cell type and that during later development other factors influence cell fate.
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PMID:Initial cell-type choice in a simple eukaryote: cell-autonomous or morphogen-gradient dependent? 861 80

omega 4403 is the site of a Tn5 lac insertion in the Myxococcus xanthus genome that fuses lacZ expression to a developmentally regulated promoter. Cell-cell interactions that occur during development, including C-signaling, are required for expression of Tn5 lac omega 4403. We have cloned DNA upstream of the omega 4403 insertion site, localized the promoter, and identified a potential open reading frame. From the deduced amino acid sequence, the gene disrupted by Tn5 lac omega 4403 appears to encode a serine protease that is dispensable for development. The gene begins to be expressed between 6 and 12 h after starvation initiates development, as determined by measuring mRNA or beta-galactosidase accumulation in cells containing Tn5 lac omega 4403. The putative transcriptional start site was mapped, and sequences centered near -10 and -35 bp relative to this site show some similarity to the corresponding regions of promoters transcribed by Escherichia coli sigma70 RNA polymerase. However, deletions showed that an essential promoter element lies between -80 and -72 bp, suggesting the possible involvement of an upstream activator protein. DNA downstream of -80 is sufficient for C-signal-dependent activation of this promoter. The promoter is not fully expressed when fusions are integrated at the Mx8 phage attachment site in the chromosome. Titration of a limiting factor by two copies of the regulatory region (one at the attachment site and one at the native site) can, in part, explain the reduced expression. We speculate that the remaining difference may be due to an effect of chromosomal position. These results provide a basis for studies aimed at identifying regulators of C-signal-dependent gene expression.
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PMID:Characterization of the regulatory region of a cell interaction-dependent gene in Myxococcus xanthus. 862 20

Transposon insertions that stabilize the beta-galactosidase activity of a HemA-LacZ hybrid protein following carbon starvation were mapped to the atp operon of Salmonella typhimurium. This effect is similar to that seen with nuo mutants defective in the energy-conserving type I NADH dehydrogenase. Insertions in several other genes, including such highly pleiotropic mutants as rpoS, polA, and hfq, were isolated with the same phenotypic screen, but they do not affect the beta-galactosidase activity of HemA-LacZ. All of these mutants act indirectly to alter the colony color of many different fusion strains on indicator plates.
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PMID:Stabilization of a HemA-LacZ hybrid protein against proteolysis during carbon starvation in atp mutants of Salmonella typhimurium. 863 58

Genes whose expression is regulated by sulfate starvation in Escherichia coli were identified by generating random translational lacZ fusions in the chromosome with the lambda placMu9 system. Nine lacZ fusion strains which expressed beta-galactosidase after growth under sulfate starvation conditions but not after growth in the presence of sulfate were found. These included two strains with insertions in the dmsA and rhsD genes, respectively, and seven strains in which the insertions were located within a 1.8-kb region downstream of hemB at 8.5 minutes on the E. coli chromosome. Analysis of the nucleotide sequence of this region indicated the presence of four open reading frames designated tauABCD. Disruption of these genes resulted in the loss of the ability to utilize taurine (2-aminoethanesulfonate) as a source of sulfur but did not affect the utilization of a range of other aliphatic sulfonates as sulfur sources. The TauA protein contained a putative signal peptide for transport into the periplasm; the TauB and TauC proteins showed sequence similarity to ATP-binding proteins and membrane proteins, respectively, of ABC-type transport systems; and the TauD protein was related in sequence to a dichlorophenoxyacetic acid dioxygenase. We therefore suggest that the proteins encoded by tauABC constitute an uptake system for taurine and that the product of tauD is involved in the oxygenolytic release of sulfite from taurine. The transcription initiation site was detected 26 to 27 bp upstream of the translational start site of tauA. Expression of the tauD gene was dependent on CysB, the transcriptional activator of the cysteine regulon.
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PMID:Identification of sulfate starvation-regulated genes in Escherichia coli: a gene cluster involved in the utilization of taurine as a sulfur source. 880 33

Production of the two phospholipases C (PLCs) in Pseudomonas aeruginosa PAO1 is induced under conditions of phosphate limitation, or by the osmoprotectants choline or glycine betaine. Tn5 mutagenesis was performed on strain PAO1 to isolate mutants deficient in choline-dependent induction of PLC. Two mutants, Tn5T1 and Tn5G19, were identified which produce decreased levels of PLC in phosphate-replete media supplemented with choline. A total of 136 and 496 bp of flanking DNA from Tn5G19 and Tn5T1 was cloned by an inverse polymerase chain reaction (PCR) and sequenced. The DNA flanking the Tn5T1 insertion contains an open reading frame predicted to encode a peptide that is approx. 60% identical to the N-terminus of a previously identified protein (P35) of unknown function from Escherichia coli. The P35 gene, which is located in the nusA-infB operon in E. coll, was designated orp (osmoprotectant regulator of PLC). Haemolytic titres, total PlcH protein and beta-galactosidase activity expressed from a chromosomally inserted plcH-lacZ operon fusion were reduced in strain Tn5T1 in comparison with the parental strain (PAO1) carrying the same fusion. However, this mutant expressed several-fold higher levels of plcH message than strain PAO1 in the presence of choline, while the phosphate-starvation-dependent transcript of plcH could not be detected in this mutant. The defects in Tn5T1 are complemented by a DNA fragment, isolated from a genomic library of PAO1, that carries the orp gene. The deduced amino acid sequence of the DNA fragment cloned from Tn5G19 exhibits 84% identity with the betB gene product of E. coli that has betaine aldehyde dehydrogenase activity. This enzyme catalyses the conversion of betaine aldehyde to glycine-betaine. Unlike the parental strain, the Tn5G19 mutant could not utilize choline as a sole carbon, nitrogen and energy source, and it was deficient in betaine aldehyde dehydrogenase activity. Also, consistent with a disruption of betB in Tn5G19, choline inhibited growth of this strain in media containing 0.7 M NaCl, while glycine-betaine restores growth to wild-type levels. The defects in Tn5G19 are complemented by a DNA fragment from PAO1 that carries the betB gene. The orp gene is located between 0.6 to 6.6 min while betB is located between 10.5 to 12.5 min on the chromosome of PAO1.
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PMID:Molecular characterization of mutants affected in the osmoprotectant-dependent induction of phospholipase C in Pseudomonas aeruginosa PAO1. 900 19

Sequence data for genes encoding 16S rRNA indicated that the marine strain previously named Pseudomonas sp. strain S9 would be better identified as a Pseudoalteromonas sp. By use of transposon mutagenesis, a chitinase-negative mutant of S9 with a lacZ reporter gene insertion was isolated. Part of the interrupted gene was cloned and sequenced. The deduced amino acid sequence had homology to sequences of bacterial chitinases. Expression of the chitinase gene promoter was quantified by measuring the lacZ reporter gene product, beta-galactosidase, beta-Galactosidase production was induced 10-fold by N-acetylglucosamine and 3-fold by chitin in minimal medium. Repression of beta-galactosidase synthesis was observed in rich medium either with or without chitin but was not observed in minimal medium containing glucose. The chitinase gene promoter was induced by starvation and higher-than-ambient levels of carbon dioxide but not by cadmium ion, heat or cold shock, or UV exposure.
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PMID:Use of a promoterless lacZ gene insertion to investigate chitinase gene expression in the marine bacterium Pseudoalteromonas sp. strain S9. 925 Nov 87

Genetic engineering of wine yeast strains requires the identification of gene promoters specifically activated under wine processing conditions. In this study, transcriptional activation of specific genes was followed during the time course of wine fermentation by quantifying mRNA levels in a haploid wine strain of Saccharomyces cerevisiae grown on synthetic or natural winery musts. Northern analyses were performed using radioactive probes from 19 genes previously described as being expressed under laboratory growth conditions or on molasses in S. cerevisiae during the stationary phase and/or under nitrogen starvation. Nine genes, including members of the HSP family, showed a transition-phase induction profile. For three of them, mRNA transcripts could be detected until the end of the fermentation. Expression of one of these genes, HSP30, was further studied using a HSP30::lacZ fusion on both multicopy and monocopy expression vectors. The production of beta-galactosidase by recombinant cells was measured during cell growth and fermentation on synthetic and natural winery musts. We showed that the HSP30 promoter can induce high gene expression during late stationary phase and remains active until the end of the wine fermentation process. Similar expression profiles were obtained on five natural winery musts.
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PMID:Stationary-phase gene expression in Saccharomyces cerevisiae during wine fermentation. 927 Nov 6

The signal transduction cascade initiated by the activation of phosphoinositide 3-kinase (PI-3 kinase) is implicated in mitogenic and antiapoptotic signaling generated by growth factors in a variety of cell types. We have examined the consequences of an inhibition of this pathway in human diploid fibroblasts. We find that a specific PI-3 kinase inhibitor (LY294002) causes growth arrest in these cells accompanied by changes in gene expression that are similar to those seen during cellular senescence. A second inhibitor, PD58029, which is specific for the mitogen-activated protein kinase kinase 1 (MEK-1), also induces a growth arrest but does not induce the same spectrum of gene expression. The pattern of gene expression in the presence the MEK-1 inhibitor is similar to that seen during growth arrest induced by serum starvation. The specific phenotypic changes seen following inhibition of PI-3 kinase are: an increase in beta-galactosidase activity; a decrease in EPC-1 gene expression; and a dramatic increase in collagenase gene expression. Thus, growth arrest with a PI-3 kinase inhibitor induces a senescent-like phenotype that is not seen when cells are growth arrested by either serum starvation or a MEK-1 inhibitor.
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PMID:A phosphatidylinositol 3-kinase inhibitor induces a senescent-like growth arrest in human diploid fibroblasts. 981 8

The alc gene cluster of Bordetella pertussis includes three genes, alcA, alcB, and alcC, which are involved in alcaligin siderophore biosynthesis in response to iron starvation. The production of AlcA, AlcB, and AlcC in Bordetella cells and the transcriptional organization of alcA, alcB, and alcC were investigated by using a set of three alc'-'lacZ gene fusion constructs that were contiguous with the known promoter upstream of alcA and extended to fusion junctions within each alc cistron. All three alc'-'lacZ fusions exhibited iron-repressible reporter gene expression which was abolished by deletion of the 105-bp alcA promoter-operator region. In an immunoblot analysis using a monoclonal antibody specific for beta-galactosidase, the AlcA-LacZ, AlcB-LacZ, and AlcC-LacZ hybrid proteins were detected in Bordetella cells grown under iron-depleted conditions. A B. pertussis mutant in which the 105-bp alcA promoter-operator region was deleted by allelic exchange was unable to produce detectable levels of siderophore. Hybridization analysis using gene-specific probes showed that alc-specific transcript levels in the mutant were negligible compared with those of the wild-type parent. These results confirm that alcA, alcB, and alcC are cotranscribed from an iron-regulated control region immediately upstream of alcA. Transcript analysis using hybridization probes representing regions downstream of alcC demonstrated that alc transcription extends approximately 3.6 kb further downstream from the alcC coding region, suggesting the cotranscription of additional, uncharacterized alcaligin system genes.
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PMID:Transcriptional analysis of the Bordetella alcaligin siderophore biosynthesis operon. 947 39


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