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:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A family of hybrid plasmids carrying the entire gal operon of E. coli and designated pgal was constructed in vitro. In the case of pgal 1 (mol. wt. 16.4 Md), a fragment cut by Bam HI endonuclease from lambda gal phage DNA (lambda D-J-gal-att-int) was joined to pMB9 and cloned in the gal-strain of E. coli, which was grown on selective media with galactose as a sole source of carbon. Plasmid pgal2 was derived from pgal 1 by elimination of the 1.1 Md fragment located between the two EcoRI sites and carrying the lambda att-int region and part of pMB9. To obtain pgal3, the 10.7 Md fragment of lambda DNA located between the two SmaI sites (lambda D-J and part of pMB9) in pgal2 was cut out and the resulting flush-end fragments were sealed by the T4DNA ligase. The mol. wt. of pgal3 containing one SmaI site amounted to 4.6 Md, while several pgal3 variants that had lost their SmaI site were still smaller. Plasmid pgal1 inhibited the growth of the gal- host cells, which effect could be overcome by the accompanying helper pMB9. The presence of pgal2 and pgal3 supported the growth and multiplication of gal- cells on selective media even without the helper plasmid. The total amount of pgal plasmid DNA per cell was constant and equalled 60--70 Md (4 copies of pgal1 or 15--16 copies of pgal3, ColE1 or pMB9). This might explain why the co-presence of pMB9 helper does alleviate the "harmful" effects of the plasmid pgal1 (which carries att-int genes), by reducing the copy number of the latter from four to one.
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PMID:Construction and properties of hybrid plasmids carrying the E. coli gal operon. 15 51

The gal3 mutation of E. coli is an insertion of a DNA sequence, 1,100 base pairs in length, into the operator-promoter region of the galactose operon. This mutation reverts spontaneously to gal+ by excision of the insertion to produce stable, inducible revertants, or by tandem duplications of the gal operon to produce unstable, constitutive revertants. The nature of a third class of revertants, which are stable and constitutive, is the subject of the present study. The stable, constitutive class of revertants included approximately 30% of all gal+ revertants obtained from a gal3 (lambda) strain. Although the constitutive reversions could be transduced by lambda, the efficiency was found to be extremely poor and the rare transductants which did appear seemed to originate from abnormal transducing particles. It was concluded that these reversions were not normally packaged by lambda. In order to facilitate the packaging of these reversions, the chlD-pgl region was deleted from the parent gal3 (lambda) strain. Unexpectedly, the gal3 mutation in the majority of these deletions reverted to produce stable, constitutive reversions exclusively. The explanation proposed was that the chlL-pgl deletions had also removed part of the gal operator-promoter. These revertants were not considered to be true representatives of the stable, constitutive class. The specificity of deletion end-points at the insertion was found only in the gal3 (lambda) strain, and not in gal+, gal+(lambda), or gal3 strains. Moreover, the frequency of spontaneous chlD-pgl deletions increased 10- to 15-fold in presence of the gal3 insertions. A lambdagal phage bearing a true stable, constitutive reversion (galc200) was isolated from the revertant strain by subsequent deletion of the chlD-pgl segment (delta31). Electron micrographs of lambdagal+ and lambdac200 delta31(chlD pgl) DNA heteroduplexes were interpreted to indicate that the stable, constitutive reversion had arisen by a deletion of 3/4 of the gal3 insertion sequence. The main conclusions are: (i) the stable, constitutive reversions of gal3 can arise by partial deletions of the insertion sequence, apparently by elimination of the nucleotide sequence which causes polarity; (ii) the chlD-pgl deletions may exhibit preferential termination at the right extremity of the gal3 insertion in presence of prophage lambda; and (iii) the gal3 insertion appears to inhibit the production of lambdagal particles by providing a nucleotide sequence which is recognized and degraded by a specific endonuclease. It is suggested that inhibition of transducing particle formation by gal3 and the preferred termination of deletions at gal3 might represent related phenomena.
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PMID:Reversion of the gal3 mutation of Escherichia coli: partial deletion of the insertion sequence. 77 85

A series of chimeric plasmids was constructed using colicinigenic factor E1 (ColE1) DNA as the replicon and DNA fragments carrying the galactose or tryptophan operons from E. coli. Restriction endonuclease EcoRI digests of ColE1 DNA and various DNAs containing the trp or gal operons were joined by T4 polynucleotide ligase [polynucleotide synthetase (ATP), poly(deoxyribonucleotide):poly(deoxyribonucleotide) ligase (AMP-forming), EC 6.5.1.1]. Chimeric plasmids carrying the desired genes were selected after transformation of Trp- or Gal- cells with ligated DNA. By using this method, we constructed ColE1-gal and ColE1-trp chimeric plasmids in which the source of the bacterial gal and trp operons was an unfractionated EcoRI digest of total E. coli DNA. The frequency of recovery of such chimeric plasmids is 10 to 20 colonies per mug of ligated DNA used in the transformation step. The method utilized in this report for constructing specific chimeric plasmids from total E. coli DNA is very simple. It requires only endonuclease R-EcoRI and T4 polynucleotide ligase, both of which are commercially available. The yield of transformants suggests that this method will be useful for cloning and amplifying a wide variety of functionally defined genes from E. coli and other prokaryotic organisms.
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PMID:Biochemical construction of specific chimeric plasmids from ColE1 DNA and unfractionated Escherichia coli DNA. 79 75

Recombinant DNA techniques were used to insert foreign genes into bovine herpesvirus-1 [infectious bovine rhinotracheitis virus (IBRV)] vectors which were attenuated by deletion and/or insertion mutations in the IBRV thymidine kinase (tk) gene. In one recombinant, the regulatory and coding sequences of the late pseudorabies virus (PRV) glycoprotein gIII gene, were inserted into the early IBRV tk gene. This recombinant efficiently expressed the PRV gIII gene indicating that immediate early IBRV proteins were competent to transactivate the late PRV gIII gene. IBRV vector viruses were also prepared in which the coding sequences of the early PRV tk gene, the late PRV gIII gene, and the E. coli beta-galactosidase gene were ligated to the late IBRV gIII promoter. Genotypes and phenotypes of the recombinant viruses were verified by restriction endonuclease and molecular hybridization experiments, thymidine plaque autoradiography, beta-gal plaque assays, and by immunoprecipitation experiments on extracts from 3H-mannose-labelled cells. The recombinant IBRV expressing beta-gal from the IBRV gIII promoter has been useful as an intermediate in the construction of IBRV vectors harboring foreign DNA sequences. The infectivity of the IBRV recombinant that expressed PRV gIII from the IBRV gIII promoter, was neutralized by polyclonal PRV antisera and by monoclonal antibodies to PRV gIII. The PRV gIII glycoprotein synthesized by the preceding recombinant has been used to coat microtiter test plate wells in a PRV gIII differential diagnostic test kit.
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PMID:Expression of porcine pseudorabies virus genes by a bovine herpesvirus-1 (infectious bovine rhinotracheitis virus) vector. 131 33

NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is a key enzyme involved in the catabolism of the prostaglandins. The cDNA for human placental 15-PGDH has been expressed in Escherichia coli as a catalytically active protein. The polymerase chain reaction was used to introduce restriction endonuclease sites at each end of the 15-PGDH coding sequence. The 15-PGDH DNA was then inserted into the bacterial expression plasmids pUC-18 and pUC-19 which contain the isopropyl-l-thio-beta-D-galactopyranoside (IPTG) inducible lacZ promoter. Extracts from E. coli containing these expression plasmids exhibited 15-PGDH activity which was inducible with (IPTG). Crude extracts from E. coli expressing 15-PGDH activity were found to contain proteins of the predicted sizes in stained SDS-polyacrylamide gels and in Western blots using human placental 15-PGDH antiserum. The specific activity in E. coli extracts was several hundred-fold higher than that seen in extracts from human placenta.
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PMID:Expression of the cDNA for NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase as a catalytically active enzyme in Escherichia coli. 150 55

The mutational potency of apurinic/apyrimidinic (AP) sites induced by heat-treatment under acidic conditions has been studied in mammalian cells. Abasic sites were induced on a single-stranded DNA shuttle vector carrying the supF tRNA gene, eliminating, therefore, any ambiguity concerning the damaged strand. This vector was able to replicate both in mammalian cells and in bacteria where the mutations induced in animal cells on the supF tRNA gene were screened by the white/blue beta-galactosidase assay in the presence of isopropyl-1-thio-beta-D-galactopyranoside and 5-bromo-4-chloro-3-indoyl-beta-D-galactoside. All white colonies contained plasmid with a mutation on the target gene which was directly sequenced. Our results show that one AP site was induced/22 min of heating as measured by sensitivity of DNA to alkali denaturation or treatment with the AP-endonuclease activity of the FPG protein (Fapy-DNA glycosylase). Putative AP sites decrease survival of the plasmid with a lethal hit of one AP site/single-stranded molecule. Mutation frequency was increased by a factor of approximately six after 2 h at 70 degrees C. Most of the induced mutations were point mutations not distributed at random and clustered in the gene region which will give rise to the mature tRNA. Mutations were abolished by treatments that eliminated AP sites such as alkali treatment or incubation with the Fapy-DNA glycosylase protein. Under our experimental conditions, when only single mutations were taken into account, the order of base insertion opposite AP sites was G greater than A greater than T greater than C.
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PMID:Mutation spectrum of heat-induced abasic sites on a single-stranded shuttle vector replicated in mammalian cells. 152 92

The Saccharomyces cerevisiae mitochondrial endonuclease I-SceI creates a double-strand break as the initiating step in the gene conversional transfer of the omega+ intron to omega- DNA. We have expressed a galactose-inducible synthetic I-SceI gene in the nucleus of yeast that also carries the I-SceI recognition site on a plasmid substrate. We find that the galactose-induced I-SceI protein can be active in the nucleus and efficiently catalyze recombination. With a target plasmid containing direct repeats of the Escherichia coli lacZ gene, one copy of which is interrupted by a 24-bp cutting site, galactose induction produces both deletions and gene conversions. Both the kinetics and the proportion of deletions and gene conversions are very similar to analogous events initiated by a galactose-inducible HO endonuclease gene. We also find that, in a rad52 mutant strain, the repair of double-strand breaks initiated by I-SceI and by HO are similarly affected: the formation of deletions is reduced, but not eliminated. Altogether, these results suggest either that the two endonucleases act in the same way after double-strand break formation or that the two endonucleases are not involved in subsequent steps.
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PMID:Site-specific recombination determined by I-SceI, a mitochondrial group I intron-encoded endonuclease expressed in the yeast nucleus. 155 70

The chromosomally encoded galactose utilization (gal) operons of Salmonella typhimurium and S. typhi were each cloned on similar 5.5-kilobase HindIII fragments into pBR322 and were identified by complementation of Gal- Escherichia coli strains. Restriction endonuclease analyses indicated that these Salmonellae operons share considerable homology, but some heterogeneities in restriction sites were observed. Subcloning and exonuclease mapping experiments showed that both operons have the same genetic organization as that established for the E. coli gal operon (i.e., 5' end, promoter, epimerase, transferase, kinase, and 3' end). Two gal operator regions (oE and oI) of S. typhimurium, identified by repressor titration in an E. coli superrepressor [galR(Sup)] mutant, were sequenced and found to flank the promoter region. This promoter region is identical to the -10 and -35 regions of the E. coli gal operon. Minicell studies demonstrated that the three gal structural genes of S. typhimurium encode separate polypeptides of 39 kilodaltons (kDa) (epimerase, 337 amino acids [aa's]), 41 kDa (transferase, 348 aa's), and 43 kDa (kinase, 380 aa's). Despite functional and organizational similarities, DNA sequence analysis revealed that the S. typhimurium gal genes show less than 70% homology to the E. coli gal operon. Because of codon degeneracy, the deduced amino acid sequences of these polypeptides are highly conserved (greater than 90% homology) as compared with those of the E. coli gal enzymes. These studies have defined basic genetic parameters of the gal genes of two medically important Salmonella species, and our findings support the hypothesized divergent evolution of E. coli and Salmonella spp. from a common ancestral parent bacterium.
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PMID:Molecular cloning and physical and functional characterization of the Salmonella typhimurium and Salmonella typhi galactose utilization operons. 219 56

A genetically engineered lac repressor/T7 endonuclease hybrid protein shows repressor-like binding toward restriction fragments carrying the lac operator. In addition, fragments carrying the operator near a particular pBR322 sequence are cleaved into specific products. Cleavage occurs at precise positions within that sequence, is independent of the orientation of the operator, is inhibited by isopropyl-1-thio-beta-D-galactopyranoside, and is observed when the target is separated from the operator by at least as few as 150 and as many as 240 base pairs. This evidence indicates that the hybrid protein is a site-directed nuclease that requires the following two structural elements for activity: the lac operator and a target. Repressor-like binding directs the enzyme to the operator and nearby single-stranded DNA targets. The discovery of an unusual target in a well-studied DNA sequence is evidence of the power of this approach for probing unusual structures in non-supercoiled duplex DNA.
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PMID:A site-targeted recombinant nuclease probe of DNA structure. 278 52

The amino acid composition and NH2-terminal amino acid sequence of barley nuclease (EC 3.1.30.2) were determined. The amino acid composition is similar to that of mung bean nuclease, and therefore the biochemical properties of barley nuclease were characterized and compared with those of mung bean and other plant nucleases. The 3'-nucleotidase activity of barley nuclease is greater for purine than for pyrimidine ribonucleotides. The enzyme has little activity towards ribonucleoside 2' and 5'-monophosphates, and deoxyribonucleoside 3' and 5'-monophosphates, and is also inactive towards the 3'-phosphoester linkage of nucleoside cyclic 2',3' and 3',5'-monophosphates. The enzyme hydrolyzes dinucleoside monophosphates, showing strong preference for purine nucleosides as the 5' residues. Barley nuclease shows significant base preference for homoribonucleic acids, catalyzing the hydrolysis of polycytidylic acid greater than polyuridylic acid greater than polyadenylic acid much greater than polyguanylic acid. The enzyme also has preference for single-stranded nucleic acids. Hydrolysis of nucleic acids is primarily endonucleolytic, whereas the products of digestion possess 5'-phosphomonoester groups. Nuclease activity is inhibited by ethylenediaminetetraacetic acid and zinc is required for reactivation. Secretion of nuclease from barley aleurone layers is dependent on the hormone gibberellic acid [Brown, P.H. and Ho, T.-h. D. (1986) Plant Physiol. 82, 801-806]. Consistent with these results, gibberellic acid induces up to an eight-fold increase in the de novo synthesis of nuclease in aleurone layers. The secreted enzyme is a glycoprotein having an apparent molecular mass of 35 kDa. It consists of a single polypeptide having an asparagine-linked, high-mannose oligosaccharide. The protein portion of the molecule has a molecular mass of 33 kDa.
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PMID:Biochemical properties and hormonal regulation of barley nuclease. 282 11


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