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)

We have constructed and purified by affinity chromatography three beta-galactosidase (beta Gal) fusion proteins (BSB133, BSBCD8, and BGA134) containing amino acid (aa) sequences from Aspergillus glucoamylase (GA). BSB133, containing the C-terminal 133 aa of GA (aa 484-616), adhered to native starch granules with a much higher affinity (Kad = 18 ml/g starch) than a beta Gal control (Kad = 0.9 ml/g starch). Two other fusion proteins, BSBCD8 and BGA134, similar in size to BSB133, adhered to starch with a relatively low affinity (Kad = 7 ml/g starch, and Kad = 4 ml/g starch, respectively). BSBCD8 differs from BSB133 by a truncation of 8 aa at the C terminus. BGA134 contains 134 aa from an overlapping region of GA (aa 380-513). These results confirm the presence of a strong starch-binding region (SBR) included in the C-terminal 133 aa of GA and indicate that the SBR can confer starch-binding activity on a fusion protein produced in Escherichia coli. In the presence of crude soluble cell extracts, the fusion proteins adsorbed by native starch granules with an affinity similar to that of the purified enzymes. BSB133 that had been adsorbed by starch from crude extracts could be eluted at a high level of purity, similar to that achieved by affinity chromatography. These results suggest that it may be feasible to use native starch as an adsorbent for the recovery and purification of recombinant fusion proteins containing the SBR. Starch has many favorable qualities for this application: it is inexpensive, stable, nontoxic, and easy to recover by centrifugation.
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PMID:Adsorption to starch of a beta-galactosidase fusion protein containing the starch-binding region of Aspergillus glucoamylase. 190 29

A simple quantitative bioassay for infectious HIV-1 has been developed. The assay is based on adherent CD4+ HeLa cell lines stably transfected with episomal vectors carrying the Escherichia coli beta-galactosidase gene under the control of the HIV long terminal repeat (LTR) promoter. HIV infection of these cell lines transactivates the LTR promoter inducing beta-galactosidase production. Infected cells and virus foci can be stained dark blue by the addition of the chromogenic substrate X-Gal. Alternatively, a readily automatable quantitative enzyme assay can be performed on the infected cultures. Because of its simplicity the bioassay may be useful for routine quantification of HIV-infected cultures, plaque purification, virus neutralization studies and for the screening of antiviral agents.
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PMID:HIV-1 indicator cell lines. 190 60

The spontaneous differentiation of CaCo-2 human colonic adenocarcinoma cells to enterocytes in culture is associated with a decrease in polylactosaminoglycans, particularly those attached to the lysosomal membrane glycoprotein h-lamp-1 (Youakim et al., Cancer Res., 49:6889-6895, 1989). To elucidate the biosynthetic mechanisms leading to these alterations we have compared glycosyltransferase activities that are involved in the synthesis of polylactosaminoglycans and of the N- and O-glycan structures that provide the framework for the attachment of these chains. Glycosyltransferase activities in cell homogenates obtained from undifferentiated and differentiated CaCo-2 cells were assayed by high pressure liquid chromatography separation of enzyme products. The beta-galactosidase activities and extremely high pyrophosphatase activities in differentiated cells were effectively inhibited by 5 mM gamma-galactonolactone and 10 mM AMP, respectively. CaCo-2 cells contain most of the enzymes that are involved in N-glycan branching [N-acetylglucosamine (GlcNAc) transferases I to V] with the exception of GlcNAc transferase VI. The levels of GlcNAc transferase I activities were comparable in undifferentiated and differentiated cells, but GlcNAc transferase II to V activities were significantly increased upon differentiation. The enzyme activities that are directly involved in the synthesis of linear polylactosaminoglycans (Gal beta 4GlcNAc beta 3- repeating units), blood group i UDP-GlcNAc:Gal beta-R beta 3-GlcNAc transferase and UDP-Gal:GlcNAc beta 4-Gal transferase, were found at similar levels in undifferentiated and differentiated CaCo-2 cells. Since GlcNAc transferase III activity is known to inhibit further branching and galactosylation, these results suggest that its increased activity in differentiated CaCo-2 cells may be partly responsible for the decreased synthesis of fucosylated polylactosaminoglycans. Differentiated cells showed a 2-fold increase in O-glycan core 2 UDP-GlcNAc:Gal beta 3GalNAc alpha-R [GlcNAc to N-acetylgalactosamine (GalNAc)] beta 6-GlcNAc transferase activity. In contrast, O-glycan core 1 UDP-Gal:GalNAc alpha-R beta 3-Gal transferase activity was found decreased. Several enzymes that are found in homogenates from normal human colonic tissue are absent or barely detectable in CaCo-2 cells. These include blood group I UDP-GlcNAc:GlcNAc beta 3Gal beta-R (GlcNAc to Gal) beta 6-GlcNAc transferase, O-glycan core 3 UDP-GlcNAc:GalNAc alpha-R beta 3 GlcNAc transferase and O-glycan core 4 UDP-GlcNAc:GlcNAc beta 3GalNAc-R (GlcNAc to GalNAc) beta 6-GlcNAc transferase.
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PMID:Glycosyltransferase changes upon differentiation of CaCo-2 human colonic adenocarcinoma cells. 190 2

The previously reported FACS-Gal assay (Nolan et al., Proc Natl Acad Sci USA 85:2603-2607, 1988) measures E. coli lacZ-encoded beta-galactosidase activity in individual viable eukaryotic cells for a variety of molecular and cellular biological applications. Enzyme activity is measured by flow cytometry, using a fluorogenic substrate, which is hydrolyzed and retained intracellularly. In this system, lacZ serves both as a reporter gene to quantitate gene expression and as a selectable marker for the fluorescence-activated sorting of cells based on their lacZ expression level. This report details the following improvements of the original assay: 1) use of phenylethyl-beta-D-thiogalactoside, a competitive inhibitor, to inhibit beta-galactosidase activity; 2) reduction of false positives by two-color measurements; and 3) inhibition of interfering mammalian beta-galactosidases by the weak base chloroquine. We found an exponential relationship between fluorescence generated by beta-galactosidase in this assay and the intracellular concentration of beta-galactosidase molecules. Finally, we report conditions for optimal loading of the substrate (FDG) and retention of the product, fluorescein. Under these conditions, we found uniform loading of FDG in all cells of a clone in individual experiments. Together, these improvements make FACS-Gal an extremely powerful tool for investigation of gene expression in eukaryotic cells.
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PMID:Improved FACS-Gal: flow cytometric analysis and sorting of viable eukaryotic cells expressing reporter gene constructs. 190 92

A beta-galactosidase was extracted from the internal organs of a sea squirt, Styela plicata, and purified 959-fold, with an 18% yield, by successive gel chromatography, anion-exchange chromatography, chromatofocusing, and affinity chromatography on a Con A-Sepharose column. The purified enzyme was fairly homogeneous, as judged on disc PAGE, SDS-PAGE, and gel chromatography on a Sephadex G-200 column. The molecular weight of the enzyme was estimated to be 77,000 and 75,000 by gel chromatography and SDS-PAGE, respectively, and its isoelectric point was determined to be 4.9 by the isoelectric focusing method. The enzyme was substantially stable in the pH range of 3.5 to 7.5, the optimum pH being 4.0. The enzyme was significantly inhibited by 9 mM HgCl2 and 9 mM DFP, while the inhibition by 0.9% PCMB was only 60% at 0 degrees C for 30 min. The purified beta-galactosidase apparently liberated galactose from a sea squirt antigen (H-antigen), two allergenically active glycopeptides (Gp-1 and Gp-2) derived from another sea squirt antigen (Gi-rep), asialo-ovomucoid glycopeptide, asialo-fetuin glycopeptide, GA1, CDH, and an ABEE-derivative (Gal beta 1----3ThrNAc-ABEE) of Gal beta 1----3GalNAc-ol isolated from bovine submaxillary gland mucin.
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PMID:Purification and characterization of a sea squirt beta-galactosidase. 193 20

The cerebellum has many properties that make it a useful model for investigating neural development. Purkinje cells, the major output neurons of the cerebellar cortex, have drawn special attention because of the availability of biochemical markers and mutants that affect their development. The spatial expression of L7, a protein specific for Purkinje cells, and L7 beta Gal, a gene expressed in transgenic mice that was constructed from the L7 promoter and the marker beta-galactosidase, delineated bands of Purkinje cells that increased in number during early postnatal development. Expression of the transgene in adult reeler mutant mice, which show inverted cortical lamination, and in primary culture showed that the initial expression of L7 is intrinsic to Purkinje cells and does not depend on extracellular signals. This may reflect an underlying developmental map in cerebellum.
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PMID:Dynamic organization of developing Purkinje cells revealed by transgene expression. 194 52

In wild-type Escherichia coli, expression of the gal operon is negatively regulated by the Gal repressor and is induced 10- to 15-fold when the repressor is inactivated by an inducer. In strains completely deleted for galR, the gene which encodes the Gal repressor, the operon is derepressed by only 10-fold without an inducer. But this derepression is increased further by threefold during cell growth in the presence of an inducer, D-galactose or D-fucose. This phenomenon of extreme induction in the absence of Gal repressor is termed ultrainduction--a manifestation of further inducibility in a constitutive setup. Construction and characterization of gene and operon fusion strains between galE and lacZ, encoding beta-galactosidase as a reporter gene, show that ultrainduction occurs at the level of transcription and not translation. Transcription of the operon, from both the cyclic AMP-dependent P1 and the cyclic nucleotide-independent P2 promoters, is subject to ultrainduction. The wild-type galR+ gene has an epistatic effect on ultrainducibility: ultrainduction is observed only in cells devoid of Gal repressor protein. Titration experiments show the existence of an ultrainducibility factor that acts like a repressor and functions by binding to DNA segments (operators) to which Gal repressor also binds to repress the operon.
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PMID:Further inducibility of a constitutive system: ultrainduction of the gal operon. 200 55

AGA and AGG codons for arginine are the least used codons in Escherichia coli, which are encoded by a rare tRNA, the product of the dnaY gene. We examined the positions of arginine residues encoded by AGA/AGG codons in 678 E. coli proteins. It was found that AGA/AGG codons appear much more frequently within the first 25 codons. This tendency becomes more significant in those proteins containing only one AGA or AGG codon. Other minor codons such as CUA, UCA, AGU, ACA, GGA, CCC and AUA are also found to be preferentially used within the first 25 codons. The effects of the AGG codon on gene expression were examined by inserting one to five AGG codons after the 10th codon from the initiation codon of the lacZ gene. The production of beta-galactosidase decreased as more AGG codons were inserted. With five AGG codons, the production of beta-galactosidase (Gal-AGG5) completely ceased after a mid-log phase of cell growth. After 22 hr induction of the lacZ gene, the overall production of Gal-AGG5 was 11% of the control production (no insertion of arginine codons). When five CGU codons, the major arginine codon were inserted instead of AGG, the production of beta-galactosidase (Gal-CGU5) continued even after stationary phase and the overall production was 66% of the control. The negative effect of the AGG codons on the Gal-AGG5 production was found to be dependent upon the distance between the site of the AGG codons and the initiation codon. As the distance was increased by inserting extra sequences between the two codons, the production of Gal-AGG5 increased almost linearly up to 8 fold. From these results, we propose that the position of the minor codons in an mRNA plays an important role in the regulation of gene expression possibly by modulating the stability of the initiation complex for protein synthesis.
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PMID:Suppression of the negative effect of minor arginine codons on gene expression; preferential usage of minor codons within the first 25 codons of the Escherichia coli genes. 210 7

A transgenic mouse line was produced which allowed the expression of E. coli beta-galactosidase (beta-Gal) under the regulatory elements of the immunoglobulin heavy chain locus. Expression of the transgene is found in spleen and bone marrow. Upon immunization of the transgenic mice with beta-Gal, a reduced but clearly detectable antibody response was obtained. Affinity purification with sera from immunized transgenic mice suggests that they contain lower affinity antibodies as compared to normal littermates. Transgenic and nontransgenic mice immunized with bovine serum albumin (BSA) alone or as a mixture with beta-Gal gave comparable anti-BSA responses. Immunization with a chemically cross-linked (Gal-BSA)-protein, however, showed a 10- to 30-fold difference in the anti-BSA response. Partial unresponsiveness to beta-Gal in the transgenic mice is best explained by a dominant, peripheral suppression mechanism linked to the antigen-presenting potential of B cells.
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PMID:Partial tolerance in beta-galactosidase-transgenic mice. 211 98

We have constructed a translational fusion between the isopenicillin-N-synthetase-encoding gene (IPNS) of Aspergillus nidulans and the lacZ gene of Escherichia coli. Recombinant strains carrying a single copy of the fusion integrated at the IPNS locus produced beta-galactosidase (beta Gal) during secondary metabolism. Integration of the fusion at the argB locus results in a situation in which the only 5'-flanking sequences of the IPNS gene upstream from the chimeric fused gene are those included in the transforming plasmid. Such a strain still expresses beta Gal activity during secondary metabolism, showing that a DNA fragment including sequences of the IPNS gene from nt -2000 to +35 (relative to the translation start codon) still contains sufficient information to drive expression of the fusion gene during secondary metabolism.
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PMID:The upstream region of the IPNS gene determines expression during secondary metabolism in Aspergillus nidulans. 211 87


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