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)

Mutants of E. coli K12 with deletions of the beta-galactosidase gene (lacZ) can reacquire the ability to hydrolyze beta-galactosides during prolonged intense selection for growth on lactose. Full lactose competence is restored through a sequence of at least five mutations. Cell extracts of these derived strains hydrolyze o-nitrophenyl-beta-D-galactoside, the standard substrate for assay of beta-galactosidase. The enzyme responsible for this activity differs in its immunological, kinetic, and sedimentation characteristics from the lacZ beta-galactosidase of wild-type E. coli. Its genetic determinant, designated ebg-5, maps at 59 min on the E. coli chromosome, whereas the lac operon maps at 10 min. We suggest that a gene not involved in lactose utilization has been progressively changed into a form capable of specifying a beta-galactosidase and that this process is similar to that whereby genes with new functions are evolved by natural selection.
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PMID:Evolution of a second gene for beta-galactosidase in Escherichia coli. 412 6

A promoterless trp-lac fusion fragment was inserted near one end of the bacterial transposon Tn5 in the correct orientation to fuse lacZ gene expression to promoters outside Tn5. The resulting transposon, Tn5 lac, retains the kanamycin-resistance gene of Tn5 and transposes in Escherichia coli at 6% the frequency of Tn5 to many different sites in a bacteriophage lambda target. Expression of beta-galactosidase, the product of the lacZ gene, from Tn5 lac insertions in phage lambda depends both on insertion into a transcription unit in the correct orientation and on the regulation of the promoter of the transcription unit, verifying that by transposition Tn5 lac can fuse lacZ expression to outside promoters. An insertion of Tn5 lac in bacteriophage P1 was isolated and used to introduce Tn5 lac into Myxococcus xanthus, a bacterium that undergoes multicellular development. Stable kanamycin-resistant transductants are obtained that contain no P1 DNA sequences but have Tn5 lac inserted at different sites in the Myxococcus chromosome. Individual transductants express different levels of beta-galactosidase. A chromogenic substrate of beta-galactosidase, 5-bromo-4-chloro-3-indolyl beta-D-galactoside, is toxic in Myxococcus when cleaved in large amounts. In principle, Tn5 lac could be used to assay transcription in any bacterium in which Tn5 can transpose and beta-galactosidase can be measured.
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PMID:Construction of Tn5 lac, a transposon that fuses lacZ expression to exogenous promoters, and its introduction into Myxococcus xanthus. 609 Nov 10

A recombinant plasmid, pCB300, was constructed which carries a cauliflower mosaic virus (CaMV) DNA insert corresponding to nucleotides 1825-2280, including the coding sequence (1830-2219) of open reading frame III (ORF III). This CaMV DNA insert was fused with the amino-terminal portion of the beta-galactosidase gene. Transcription of the hybrid gene is controlled by the lac promoter, which is repressed in Escherichia coli strain JM103 and can be induced by isopropylthio-beta-D-galactoside (IPTG). When the promoter is derepressed, cells harboring the chimeric plasmid produce an Mr 16 000 fusion protein. This protein is immunodetected by antibodies raised against an amino terminal synthetic peptide of 19 amino acids corresponding to a sequence predicted from the nucleotide sequence of ORF III.
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PMID:Expression of a putative plant viral gene in Escherichia coli. 609 36

We describe a method which permits the detection of exon fragments. Such DNA was cloned and expressed in the promoter proximal part of the lac Z gene of Escherichia coli. The resulting antigen-beta-galactosidase chimeras are bound to their respective antibodies fixed to polyvinyl sheets. The beta-galactosidase part of the chimera permits detection of such clones by histochemical staining. As model DNA, we used the lac I gene cleaved with HaeIII, HhaI, or HpaII. Fragments were tailed with poly(dC) and inserted into the poly(dG)-tailed promoter proximal part of the lac Z gene. Recombinant clones, isolated on lactose-agar plates, were replica-plated and lysed with chloroform. Polyvinyl sheets coated with antibody against lac repressor were placed onto the top of the lysed colonies for immunoadsorption. The immune complexes were made visible after washing by incubation with 5-bromo-4-chloro-3-indolyl-beta-D-galactoside in buffered agar. The beta-galactosidase activity of the chimera cleaves the colourless histochemical compound to a blue dye at those positions where clones produce the antigen. In the case of the lac I gene two types of clones were isolated, carrying the NH2-terminal part of the lac repressor up to codons 27 and 75.
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PMID:Immunoenzymatic detection of expressed gene fragments cloned in the lac Z gene of E. coli. 632 87

A sensitive two-site enzyme immunoassay system for mouse beta nerve growth factor (NGF) was developed, based on the sandwiching of the antigen between anti-mouse beta NGF antibody IgG coated to a polystyrene tube and anti-mouse beta NGF antibody Fab'-linked beta-D-galactosidase (beta-D-galactoside hydrolase, EC 3.2.1.23). This method has the following advantages: (a) the procedures are simple and rapid compared to bioassay or two-site radioimmunoassay; (b) antibody Fab'-beta-D-galactosidase complex is more stable than 125I-labeled antibody; (c) purified beta NGF is detectable at a concentration as low as 10 pg/ml. Our enzyme immunoassay was used to examine the levels of NGF in some tissues of mice. The submaxillary gland contained a high concentration of NGF. However, other tissues, such as the heart, brain, and skeletal muscle, and serum did not contain detectable NGF. These results support recent findings by other investigators that NGF was not found in the organs/tissues other than the submaxillary gland of mice.
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PMID:A highly sensitive enzyme immunoassay for mouse beta nerve growth factor. 640 64

We have studied the physiological effects of mitomycin C induction on cells carrying ColE1 plasmids with differing configurations of three genes: the structural gene coding for colicin (cea), a gene responsible for mitomycin C lethality (kil) that we located as part of an operon with cea, and the immunity (imm) gene, which lies near cea but is not in the same operon. kil is close to or overlaps imm. When cea(+) plasmids are present mitomycin C induction results in 100-fold or greater increases in the level of colicin. Within an hour after induction more than 90% of cells carrying cea(+)kil(+) plasmids are killed and macromolecular synthesis stops, capacity for transport of proline, thiomethyl beta-D-galactoside, and alpha-methyl glucoside is lost, and the membrane becomes abnormally permeable as indicated by an increased accessibility of intracellular beta-galactosidase to the substrate o-nitrophenyl beta-D-galactoside. All of these events occur when a cea(-)kil(+)imm(+) plasmid is present and none does when the plasmid is cea(+)kil(-)imm(+), so the damage can be attributed solely to the Kil function and not to the presence of colicin. However, cells carrying a cea(+)kil(-)imm(-) plasmid are killed upon induction, apparently by action of endogenous colicin on the nonimmune cytoplasmic membrane. The pattern of accompanying physiological damage is distinguished from the kil(+)-associated damage by an enhancement of alpha-methyl glucoside uptake and accumulation and efflux of alpha-methyl glucoside 6-phosphate and by an absence of the alteration in membrane permeability for o-nitrophenyl beta-D-galactoside. These features are typical of colicin E1 action on the membrane. The induced damage is not prevented by trypsin and occurs in cells of a strain specifically tolerant to exogenous colicin E1, indicating that the attack is from inside the cell.
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PMID:Alternative forms of lethality in mitomycin C-induced bacteria carrying ColE1 plasmids. 640 39

Extra-embryonic endoderm cells from gastrulating chick embryos possess Ca2+-dependent and Ca2+-independent adhesive mechanisms. These cells also contain an endogenous beta-D-galactoside-binding lectin and cell surface receptors bearing galactose groups. The endogenous lectin inhibits cellular adhesion. To test whether the adhesive interactions involving lectin and galactose molecules are part of the Ca2+-independent or Ca2+-dependent adhesive mechanism, dissociated cells which were preincubated in beta-galactosidase were allowed to aggregate in the presence and absence of Ca2+ ions. Significant decreases in adhesion were observed in both cases. Cells were also allowed to aggregate in the presence and absence of Ca2+ ions when blastoderm lectin was present in the medium. Adhesion was decreased in both cases. The results suggest that cell surface galactose groups and the beta-D-galactoside-binding lectin are involved in Ca2+-independent adhesion.
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PMID:Calcium-independent adhesion of extra-embryonic endoderm cells from the early chick blastoderm is inhibited by the blastoderm beta-D-galactoside-binding lectin and by beta-galactosidase. 640 23

Expression of the Escherichia coli lactose operon in Rhizobium meliloti 104A14 made the cells sensitive to the addition of the beta-galactosides lactose, phenyl-beta-D-galactoside, and lactobionic acid. Growth stopped when the beta-galactoside was added and viability decreased modestly during the next few hours, but little cell lysis was observed and the cells appeared normal. Protein synthesis was not inhibited. Growth was inhibited only when beta-galactosidase expression was greater than 160 U. Lactose-resistant mutants had defects in the plasmid-carried E. coli beta-galactosidase or beta-galactoside permease and in the R. meliloti genome. We speculate that uncontrolled production of galactose by the action of the lactose operon proteins was responsible for growth inhibition.
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PMID:Lactose inhibits the growth of Rhizobium meliloti cells that contain an actively expressed Escherichia coli lactose operon. 642 92

In search of a beta-galactosidase which specifically hydrolyses beta 1----3 bound galactose residues in galacto-glycoconjugates, an acid beta-galactosidase from chicken liver was investigated. The isolation procedure involved ammonium sulphate precipitation followed by lectin chromatography on Con A-Sepharose 4B, ion-exchange chromatography on DEAE-cellulose, gel filtration on Sepharose 6B and affinity chromatography on p-aminophenyl-thio-beta-D-galactoside-agarose. The beta-galactosidase was purified 3000-fold with 11% recovery of enzyme activity. The purified protein showed an apparent molecular mass of above 200000 in SDS-polyacrylamide gel electrophoresis. A few minor bands were also present. The reduced and denatured beta-galactosidase migrated as a single major band with an apparent molecular mass of 67000. The enzyme released galactose from lactose and from the synthetic substrates Gal beta 1----3Gal, Gal beta 1----6Gal and Gal beta 1----3Ara. However, the enzyme did not release galactose from the snail gland galactans and the high molecular weight galacto-glycoconjugates and it did not hydrolyse the peanut agglutinin receptor of the red blood cell membrane.
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PMID:Isolation of a beta-galactosidase from chicken liver. 644 30

The available cytochemical methods for localization of beta-galactosidase have been evaluated using pollen grains of Brassica campestris. beta-Galactosidase-deficient pollen (gal), served as a control. Azo dye methods involving naphthyl substrates showed high and nonspecific background staining to the exine. The indigogenic method, employing 5-bromo-4-chloro-3-indoxyl beta-D-galactoside (X-gal) as the enzyme substrate, gave specific opaque-blue final reaction product, while mutant pollen grains remained colourless. Final reaction product formation was blocked by D-galactono-1,4-lactone, thus demonstrating the specificity of the enzyme reaction. Using microspectrophotometry, the absorbance of the final reaction product was found to be a linear function of incubation time and section thickness in cryostat sections up to 8 micron thick and was only slightly reduced by glutaraldehyde prefixation. The validity of the indigogenic method for quantitative analysis was confirmed by using an enzyme-containing polyacrylamide gel model system and enzyme-coupled Sepharose 4B beads. Cellular sites of enzymic activity have been determined using plastic sections: final reaction product occurred in the intine wall layer and peripheral cytoplasm.
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PMID:Quantitative cytochemistry of beta-galactosidase in normal and enzyme deficient (gal) pollen of Brassica campestris: application of the indigogenic method. 644 87


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