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 gene encoding the human immunodeficiency virus-1 (HIV-1) TAT protein was chemically synthesized and expressed in HeLa cells and in a cell-free system. To facilitate both the assembly of the synthetic gene and further mutagenesis and gene fusion studies, several unique restriction endonuclease cleavage sites were included in the coding sequence without altering the encoded protein sequence. The synthetic TAT coding sequence was fused to a translation start signal and placed under SV40 early transcriptional control. Co-transfection of the TAT-encoding synthetic gene together with a reporter gene (chloramphenical acetyl transferase or beta-galactosidase) linked to an HIV LTR confirmed that the synthetic gene product exhibits similar activity to TAT expressed from HIV genomic DNA in the transactivation of the LTR. TAT mRNA prepared by cell-free transcription of the synthetic TAT coding sequence was also shown to produce functional TAT following microinjection into HeLa-derived cells containing an integrated reporter gene with the HIV LTR linked to beta-galactosidase.
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PMID:Chemical synthesis and expression of a gene encoding HIV-1 TAT protein. 254

Since HIV tat function is essential for the HIV infectious cycle, it represents an important possible target of therapeutic intervention for HIV infection. Stable human cell lines were derived that express high levels of beta-galactosidase under the combined control of the transacting HIV-1 tat gene product and the cis-acting HIV-1 LTR. The tat gene product induces LTR-linked gene expression approximately 1000-fold in this system. The high level of expression of beta-galactosidase under HIV tat and LTR control in stable cell lines allows rapid spectrophotometric quantitation of beta-galactosidase enzymatic activity from fewer than 5000 cells seeded in a microtiter plate well. Such cell lines provide a virus-free system for the high-capacity screening of compounds for the ability to interfere with HIV tat-mediated transactivation of gene expression.
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PMID:Stable indicator cell lines exhibiting HIV-1 tat function. 254 31

Aspergillus niger tryptophan auxotrophic mutants have been isolated after UV irradiation of conidiospores. The mutants belong to two different complementation groups, trpA and trpB, which complement each other in heterokaryons. Neither of the mutations could be complemented with the cloned A. niger trpC gene. To obtain A. niger trpC mutants in a direct way, gene inactivation by cotransformation was performed. For this purpose an in-frame gene fusion between the A. niger trpC and Escherichia coli lacZ genes was constructed and shown to be functionally expressed after introduction into A. niger by cotransformation with the pyrA gene as selective marker. Among the beta-galactosidase expressing cotransformants, obtained with either circular or linearized vectors, no trpC mutants were detected, even after enrichment. Such mutants, however, could be obtained by cotransformation of A. niger with specific fragments of the fusion gene. Biochemical analysis of the cotransformants indicated that in nearly all cases the fusion gene had replaced the wild-type trpC gene. Genetic analysis showed that the trpC mutation is not linked to any of the A. niger loci described so far. The trpC mutants can be complemented by the cloned A. niger trpC gene as well as by the A. nidulans trpC gene.
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PMID:Tryptophan auxotrophic mutants in Aspergillus niger: inactivation of the trpC gene by cotransformation mutagenesis. 261 62

The beta-galactosidase-based assay for lysine developed by Tuffnell & Payne was used to measure the bioavailabilities of cyst(e)ine, methionine, threonine and tryptophan in pronase digests of 17 foods. The digests were assayed by estimating the beta-galactosidase synthesis responses of five Escherichia coli mutants, each requiring one of the respective amino acids for protein synthesis. Deletion mutants were used whenever possible in order to ensure strain stability. Single digests of each food were assayed with 3 or 4 separate cultures of each mutant and the results were compared with those from the corresponding chemical assay. Omitting the anomalously low values for one food, the rank correlation coefficients of the bio- and chemo-assay values were 0.61 (cysteine), 0.91 (lysine), 0.95 (methionine), 0.64 (threonine) and 0.85 (tryptophan). Mean (+/- S.D.) relative amino acid bioavailabilities (casein = 100%) for the 17 foods were: cysteine, 53 +/- 23; lysine, 90 +/- 10; methionine, 95 +/- 18; threonine, 89 +/- 13; and tryptophan, 89 +/- 25. The cysteine mutant appeared to give unusually low bioavailability values except for the milk products. These amino acid mutants afford a rapid method for assaying the bioavailabilities of at least four of the five amino acids studied.
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PMID:The use of Escherichia coli mutants to measure the bioavailability of essential amino acids in foods. 265 34

Defective transducing phages carrying aroG, the structural gene for phenylalanine (phe)-inhibitable phospho-2-keto-heptonate aldolase (EC 4.1.2.15; previously known as 3-deoxy-D-arabinoheptulosonate-7-phosphate synthetase[phe]), have been isolated, and DNA from two of these phages has been used to construct a restriction map of the region from att lambda to aroG. A 7.6-kb PstI-HindIII fragment from one of these phages was cloned into pBR322 and shown to contain aroG. The location of aroG within the 7.6 kb was established by subcloning and Tn3 transpositional mutagenesis. A fragment carrying the aroG promoter and operator has been cloned into a high copy number promoter-cloning vector (pMC489), and the resulting aroGpo-LacZ' (alpha) fusion subcloned in a low copy number vector. Strains with this fusion on the low copy number vector exhibit negative regulation of beta-galactosidase expression by both phenylalanine and tryptophan and positive regulation by tyrosine in a tyrR+ background.
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PMID:Cloning of aroG, the gene coding for phospho-2-keto-3-deoxy-heptonate aldolase(phe), in Escherichia coli K-12, and subcloning of the aroG promoter and operator in a promoter-detecting plasmid. 286 Nov 43

A total of 32 strains of the family Leptospiraceae (23 strains of Leptospira interrogans, 6 strains of Leptospira biflexa, 2 strains of Leptonema and 1 strain of Leptospira parva) were examined for enzyme activities using 89 substrates (API ZYM system). More than 90% of the strains belonging to the family Leptospiraceae possessed strong activities of beta-D-galactosidase, beta-D-glucosidase and 5 esterases (C5, C6, C8, C9 and C10). More than 90% of the strains belonging to the genus Leptospira, except L. parva, had strong activities of L-lysine arylamidase and alpha-L-glutamate arylamidase. L. biflexa strains, except serovar andamana, were different from the other strains examined in that they possessed glycyl-glycine arylamidase, glycyl-phenylalanine arylamidase and L-tryptophan arylamidase. L. biflexa strains, except andamana, L. parva and Leptonema strains possessed strong activities of glycine arylamidase and leucyl-glycine arylamidase. Two strains of the genus Leptonema were different from the strains belonging to the genus Leptospira in that they possessed strong activities of beta-D-lactosidase. L. parva lacked alpha-D-galactosidase which other strains belonging to the family Leptospiraceae possessed. Dendrogram analysis revealed that strains belonging to the family Leptospiraceae were divided into 4 groups. The first group consisted of all strains belonging to L. interrogans and serovar andamana of L. biflexa; the second group consisted of the remaining 5 serovars of L. biflexa; the third group consisted of the genus Leptonema; and the fourth group consisted of only L. parva.
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PMID:Enzyme activities of the strains belonging to family Leptospiraceae detected by the API ZYM system. 289 26

Out of carcinogenic heterocyclic amines, which are produced by pyrolysis of tryptophan in food, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) were found to reduce the activity of enzymes related to catecholamine metabolism in clonal rat pheochromocytoma PC12h cells. By 6 days' culture in the presence of 10 nM to 10 microM Typ-P-1 and -2, these heterocyclic amines were accumulated in the cells, and activity of tyrosine hydroxylase (TH) and aromatic L-aminoacid decarboxylase (AADC) were reduced markedly. Reduction of these enzyme activity was observed with Trp-P-1 and -2 at the concentrations lower than 1 microM, while cell protein and enzyme activity of a non-specific enzyme, beta-galactosidase were reduced only with 10 microM Trp-P-1. These results show that these heterocyclic amines are neurotoxins specific for dopaminergic neurons.
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PMID:Reduction of enzyme activity of tyrosine hydroxylase and aromatic L-aminoacid decarboxylase in clonal pheochromocytoma PC12h cells by carcinogenic heterocyclic amines. 290 12

A single-copy integration vector was used for the in vitro construction of translational fusions to the lacZ gene of Escherichia coli. Insertion of a single copy of the lacZ fusion into the B. subtilis chromosome leads to an easily detected Amy- phenotype. A trpE-lacZ fusion was constructed in which the trp promoter directs hybrid beta-galactosidase (beta Gal) synthesis. The level of beta Gal in a wild-type strain carrying the trpE-lacZ fusion in the chromosome is regulated by exogenous tryptophan, while a 5-methyltryptophan-resistant mutant constitutively synthesizes betaGal. A trpF-lacZ fusion was constructed and used to determine the effect of a frameshift mutation in the trpE gene on expression of the trpF-lacZ fusion. The frameshift mutation in trpE led to a three-fold reduction in the levels of the trpF-lacZ fusion. The levels of the betaGal activity of these integrated lacZ fusions appear to provide a quantitative measure of the expression of B. subtilis genes under single-copy conditions.
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PMID:Construction of a single-copy integration vector and its use in analysis of regulation of the trp operon of Bacillus subtilis. 301 40

Human T-cell leukemia virus type 1 (HTLV-1) is the etiologic agent of adult T-cell leukemia (ATL) and a trans-acting viral function was proposed to be involved in ATL development because of the non-specific provirus integration in leukemic cells and the frequent immortalization of helper T-cells by in vitro infection. An extra sequence "pX" in the HTLV-1 genome codes for three proteins, p40x-, p27x- and p21x-, and the p40x- is trans-activator of transcription from the viral LTR. A sequence of 21 bp repeats in the LTR was found to be an enhancer and respond to the trans-activation by p40x-. The transient expression of p40x- also activates a cellular gene for interleukin 2 receptor (IL-2R) in helper T-cell lines. This induction of IL-2R may explain the mechanism of preferential growth of HTLV-1 infected cells and may be an early event of ATL development. For practical purposes, the env gene fragments was expressed in E. coli as fusion proteins with beta-galactosidase. Using these fusion proteins, a diagnostic system detecting anti-env antibodies was developed. Immunization of monkeys with these envelope-fusion proteins protected the monkeys from the viral infection, suggesting possible usage of envelope proteins as vaccine.
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PMID:Mechanism of the gene expression of HTLV-I and its association with ATL. 303 Mar 50

The cold agglutinin isolated from the albumin gland of the snail Achatina fulica was modified with various chemical reagents in order to detect the amino acids and/or carbohydrate residues present in its carbohydrate-binding sites. Treatment with reagents considered specific for modification of lysine, arginine and tryptophan residues of the cold agglutinin did not affect the carbohydrate-binding activity of the agglutinin. Modification of tyrosine residues showed some change. However, modification with carbodiimide followed by alpha-aminobutyric acid methyl ester causes almost complete loss of its binding activity, indicating the involvement of aspartic acid and glutamic acid in its carbohydrate-binding activity. The carbohydrate residues of the cold agglutinin were removed by beta-elimination reaction, indicating that the sugars are O-glycosidically linked to protein part of the molecule. Removal of galactose residues from the cold agglutinin by the action of beta-galactosidase indicated that the galactose molecules are beta-linked. These carbohydrate-modified glycoproteins showed a marked change in agglutination property, i.e. they agglutinated rabbit erythrocytes at both 10 degrees C and 25 degrees C, indicating that the galactose residues of the glycoprotein play an important role in the cold-agglutination property of the glycoprotein. The c.d. data showed the presence of an almost identical type of random-coil conformation in the native cold agglutinin at 10 degrees C and in the carbohydrate-modified glycoprotein at 10 degrees C and 25 degrees C. This particular random-coil conformation is essential for carbohydrate-binding property of the agglutinin.
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PMID:Studies on chemical modification of cold agglutinin from the snail Achatina fulica. 311 67


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