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)

Clinical isolates of rhamnose-positive Yersinia enterocolitica (Y.e.rh+) were compared with typical rhamnose-negative Y. enterocolitica (Y.e.rh-) and with Yersinia pseudotuberculosis. The Y.e.rh+ differed from the Y.e.rh- and Y. pseudotuberculosis in their ability to ferment raffinose and lactose, utilize citrate and in their inability to grow on Hektoen enteric agar at 22 or 37 C, on Salmonella-Shigella agar at 37 C, and scant on xylose-lysine-deoxycholate agar at 37 C. An extensive temperature-dependent profile of characteristics was established for the Y.e.rh+: motility, acetoin production, citrate utilization, growth on Salmonella-Shigella agar, and ampicillin resistance occurred at 22 C but not 37 C; fermentation of melibiose, raffinose, and cellobiose occurred within 24 h at 22 C, but not before 5 days at 37 C; fermentation of rhamnose and production of beta-galactosidase occurred within 24 h at 22 C, but not before 48 h at 37 C; greater resistance to ampicillin, chloramphenicol, streptomycin, kanamycin, carbenicillin, and gentamicin was observed at 22 than 37 C; and good growth on xylose-lysine-deoxycholate agar occurred at 22 but not 37 C. For optimal recovery of Y.e.rh+ from mixed culture, e.g., stools, two MacConkey plates should be inoculated and incubated, one at 37 C, and one at 22 C. Lactose-negative colonies appearing after 48 h on the 22 C MacConkey agar but not the 37 C MacConkey agar should be considered possible Y.e.rh+. Biochemicals should be tested in duplicate, one set incubated at 22 C, one set at 37 C. Antibiotic susceptibility tests of Y.e.rh+ isolates should be incubated at both 37 C and at a lower temperature to allow the greatest expression of resistance of these organisms to the various antibiotics.
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PMID:Temperature-dependent cultural and biochemical characteristics of rhamnose-positive Yersinia enterocolitica. 125 9

Antisense oligodeoxyribonucleotides complementary to a segment of the beta-lactamase gene and containing psoralen monoadducts at specific sites were examined for their ability to make normally resistant bacteria sensitive to ampicillin. Irradiation of oligonucleotides and psoralens with long-wavelength ultraviolet radiation (380-400 nm) produced monoadducted antisense molecules. High-performance liquid chromatography was used to purify microgram quantities of photoactivatable antisense DNA. Escherichia coli transformed with a plasmid containing the gene for beta-lactamase were used to test a series of oligonucleotides containing psoralen monoadducts after additional exposure to the photoactivating effects of long-wavelength ultraviolet radiation (320-400 nm). Normally resistant bacteria treated with this photoactivatable form of antisense DNA (0.4 microM) were specifically sensitized to ampicillin. The reduction in colony formation ranged from 31 to 79% in comparison to control oligonucleotides which did not contain photoactivatable monoadduct moieties. Bacteria treated in a similar manner but in the presence of tetracycline instead of ampicillin were not affected. The activity of beta-galactosidase, whose gene is located on the same plasmid as beta-lactamase, was not affected.
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PMID:Photoactivatable antisense DNA: suppression of ampicillin resistance in normally resistant Escherichia coli. 184 55

Human growth hormone releasing factor (hGRF) gene has been synthesized and cloned. The sequence of the synthetic hGRF gene, consisting of preferred codons for expression in E. coli, was designed with the aid of computer programs. Six segments with lengths ranging from 39 to 51 nucleotides were synthesized by solid-phase phosphoramidite method. The entire gene of 141 base pairs was constructed by enzymatic ligation of all synthetic segments and then cloned into plasmid pUC-19. The positive colonies were confirmed by the screening of ampicillin resistance, inactive beta-galactosidase, and analyzing by use of restriction enzymes and dot-blot hybridization. The cloned gene was sequenced by M13 dideoxynucleotide chain termination method and proven correct.
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PMID:Chemical synthesis and cloning of the human growth hormone releasing factor gene. 213 24

Plasmid-based promoter-probe vectors pPV4 and pPV5 have been constructed which are useful for comparing the relative efficiencies of bacterial promoters. The vectors utilize the beta-galactosidase (lacZ) gene of E. coli as an indicator gene. The latter was modified using synthetic DNA fragments. The promotor-probe system contains the ampicillin resistance gene and the origin of replication of plasmid pBR322. The plasmids pPV4 and pPV5 carry clustered unique restriction sites usable for promoter insertions, and SD sequence. A synthetic DNA fragment corresponding to transcription terminator was inserted downstream the lacZ gene. Presence of the terminator made it possible to clone strong promoters controlling transcription of the lacZ gene. To prevent any undesired promotor effect, the plasmid pPV5 has also second synthetic terminator upstream from the polylinker sequence. Using this promoter-probe system, relative efficiencies of a series of synthetic promoters, including PL promoter of phage lambda and its mutant, gene X promotor of phage fd and several model statistic promoters, have been compared.
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PMID:[Construction of promoter-probe vectors on the basis of a modified beta-galactosidase gene of Escherichia coli]. 250 Sep 37

The incubation in vitro of plasmid pBR322 DNA with glucose 6-phosphate (Glc-6-P) has been shown to have a mutagenic effect when the plasmid was transformed into wild-type Escherichia coli. To further investigate the modifications of DNA by the reducing sugar Glc-6-P, we have developed an in vivo model to monitor plasmid DNA mutations. E. coli strains that are defective for phosphoglucose isomerase (strain DF40) alone or phosphoglucose isomerase and glucose-6-phosphate dehydrogenase (strain DF2000) accumulate Glc-6-P when grown in gluconate minimal medium in the presence of glucose. These strains and the control strain K10 were transformed with pAM006, a plasmid that carries the genes for ampicillin resistance and beta-galactosidase production, and grown for 24 hr under conditions that prompted the accumulation of Glc-6-P. An increase in plasmid mutations was observed (7- and 13-fold) that was associated with the increased intracellular levels of Glc-6-P (20- and 30-fold) present in the DF40 and DF2000 E. coli strains, respectively. Growth of the mutant bacteria in gluconate minimal medium does not increase the intracellular levels of Glc-6-P or the rate of plasmid mutations over background. Further characterization of the mutated plasmid DNA showed that insertions, deletions, and point mutations were responsible for the loss of beta-galactosidase production. The increase in plasmid mutations as a function of increased intracellular Glc-6-P levels suggests that the accumulation of adducts formed by Glc-6-P and other reducing sugars may contribute to DNA damage.
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PMID:Elevated glucose 6-phosphate levels are associated with plasmid mutations in vivo. 282 85

A low-copy-number vector, pFZY1, with the multiple restriction site linker of M13mp18 inserted upstream from a promoterless beta-galactosidase (beta Gal)-coding lacZ gene has been constructed to provide a convenient and accurate system to analyze regulatory elements in vivo. The plasmid contains the oriF replication origin without the par locus and is present in the cell in one to two copies per genome. It is retained in the host by the presence of ampicillin, and each inserted promoter yielded consistent values of beta Gal activity under all the conditions tested. A series of tetracycline resistance (TcR) promoter fragments and lac promoter fragments have been compared in pFZY1 and the high-copy-number pKO-vector series. The transcriptional activity measured for different fragments containing the same TcR promoter varied within a six-fold range among the several constructs tested. Regulation of the wild-type lac promoter and mutants in pFZY1 was similar to that observed for lac promoters in the chromosome while their regulation in pKO-1mp18 was significantly affected by the high copy number, as expected.
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PMID:A low-copy-number vector utilizing beta-galactosidase for the analysis of gene control elements. 303 88

pHG165, a pBR322 copy number derivative of pUC8, has a 38-bp polylinker multiple cloning site located at the 5' end of lac alpha. A further 156 bp, 3' to the multiple cloning site, completes the coding sequence for the production of the beta galactosidase alpha peptide. We describe the use of in vivo plasmid-chromosome cointegrates as a construction method that in this instance has enabled us to cross out the pHG165 multiple cloning site to obtain a wild-type beta-galactosidase sequence for the alpha peptide. Because the DNA sequence available for homologous recombination was only 156 bp in length, the frequency of crosses that removed the multiple cloning site was less than 1 x 10(-9). These crosses were easily obtained, however, after amplification by ampicillin selection.
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PMID:In vivo plasmid construction by integrative recombination within a 156 bp sequence homology. 305 1

A shuttle vector has been constructed by fusing the Bacillus subtilis trimethoprim-resistance-carrying (TpR) plasmid pNC601 with the Escherichia coli plasmid pBR322. The resultant plasmid pNBL1 can replicate in both B. subtilis and E. coli, conferring Tp resistance on both cells and ampicillin resistance (ApR) on E. coli. The B. subtilis dihydrofolate reductase operon (dfr) on pNC601 and therefore on pNBL1 consists of the thymidylate synthase B gene (thyB) and the TpR-dihydrofolate reductase gene lacking the C-terminal seven codons (designated as drfA' as compared with the complete dfrA gene). A direct-expression vector pNBL3 has been constructed by inserting synthetic oligodeoxynucleotides containing a Bacillus ribosome-binding site (RBS) and the ATG codon downstream from dfrA' on pNBL1. When the E. coli lacZ gene was placed downstream from the dfrA' gene in pNBL3, efficient synthesis of beta-galactosidase was observed in both cells, showing that the polycistronic expression system is suitable for directing expression of heterologous genes. Translational efficiency of the lacZ gene on pNBL3 was further examined in B. subtilis by changing the sequence upstream from lacZ. Unlike the results previously reported [Sprengel et al., Nucleic Acids Res. 13 (1985) 893-909], when RBS was present, the high level of lacZ expression was preserved irrespective of spacing between the stop codon of the upstream dfrA' gene and the start codon of the downstream lacZ gene. However, in the absence of RBS, the spacing between both genes affected lacZ expression. That is, translational coupling of dfrA'-lacZ was observed, although the translational efficiency was very low.
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PMID:Construction of a new shuttle expression vector for Bacillus subtilis and Escherichia coli by using a polycistronic system. 314 23

Two yeast/E. coli shuttle vectors have been constructed. The two vectors, YEp351 and YEp352, have the following properties: (1) they can replicate autonomously in Saccharomyces cerevisiae and in E. coli; (2) they contain the beta-lactamase gene and confer ampicillin resistance to E. coli; (3) they contain the entire sequence of pUC18; (4) all ten restriction sites of the multiple cloning region of pUC18 including EcoRI, SacI, KpnI, SmaI, BamHI, XbaI, SalI, PstI, SphI and HindIII are unique in YEp352; these sites are also unique in YEp351 except for EcoRI and KpnI, which occur twice; (5) recombinant plasmids with DNA inserts in the multiple cloning region of YEp351 and YEp352 can be recognised by loss of beta-galactosidase function in appropriate E. coli hosts; (6) YEp351 and YEp352 contain the yeast LEU2 and URA3 genes, respectively, allowing for selection of these auxotrophic markers in yeast and E. coli; (7) both plasmids are retained with high frequency in yeast grown under non-selective conditions indicative of high plasmid copy number. The above properties make the shuttle vectors suitable for construction of yeast genomic libraries and for cloning of DNA fragments defined by a large number of different restriction sites. The two vectors have been further modified by deletion of the sequences necessary for autonomous replication in yeast. The derivative plasmids YIp351 and YIp352 can therefore be used to integrate specific sequences into yeast chromosomal DNA.
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PMID:Yeast/E. coli shuttle vectors with multiple unique restriction sites. 333 5

Six different temperature-sensitive (ts) mutants have been isolated which have parental beta-galactoside permease levels at low temperatures but have decreased permease levels when grown at high temperatures. These mutants were derived from Escherichia coli ML308 (lacI(-)Y(+)Z(+)A(+)). After N-methyl-N'-nitro-N'-nitro-soguanidine mutagenesis, ampicillin was used to select for cells unable to grow on low lactose concentrations at 42 C. Temperature-sensitive mutants were assayed for galactoside permease activity after growth in casein hydrolysate medium at 25 or 42 C by measuring both radioactive methylthio-beta-d-galactoside uptake and in vivo o-nitrophenyl-beta-d-galactoside hydrolysis. The six conditional isolates have decreased levels of galactoside permease which are correlated with decreased growth rates at elevated temperatures. The low permease levels are not due to a temperature labile lacY gene product but rather to a temperature labile synthesis rate of functional permease. Some of the mutants exhibit a ts increase in permeability as shown by the increased leakage of intracellular beta-galactosidase and by the increased rate of in vivo o-nitrophenyl-beta-d-galactoside hydrolysis via the nonpermease mediated entry mechanism. Preliminary evidence indicates that transport in general is decreased in these mutants, yet there is some specificity in the mutational lesion since glucoside transport is unaffected. All these observations suggest that these mutants have ts alterations in membrane synthesis which results in pleiotropic effects on various membrane functions.
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PMID:Temperature-sensitive mutants of Escherichia coli affecting beta-galactoside transport. 554 36


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