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)

Plasmids were isolated from two species of Streptosporangium by CsCl-ethidium bromide equilibrium density gradient centrifugation. A plasmid isolated from S. brasiliense, designated pSgB-1, was characterized by electron microscopy and agarose gel electrophoresis. The pSgB-1 plasmid is a closed circular DNA molecule of 9.4 X 10(6) Da. A restriction endonuclease map was generated and unique cleavage sites were found for EcoRI, ClaI, XbaI, and MstII. Another plasmid, pSgV-1, isolated from S. viridognriseum, has an estimated Mr of 54 X 10(6). The pSgB-1 plasmid is phenotypically cryptic but an unusual phenotypic trait, resembling phage plaques, may be associated with the S. viridogriseum plasmid pSgV-1.
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PMID:Physical characterization of plasmids isolated from Streptosporangium. 630 3

Single turnovers of the EcoRI restriction endonuclease, cleaving its recognition site on the covalently closed form of plasmid pMB9, were examined. Two methods were used to monitor the progress of the reactions: one involved quenching the reaction at various times followed by the electrophoretic separation of the products cleaved in one and in both strands of the duplex; the other employed a stopped-flow fluorimeter to measure the amount of ethidium bromide bound to the DNA as it changes when the DNA, cleaved in at least one strand, dissociates from the enzyme. Two procedures were used to initiate the reactions. For some, one solution containing the enzyme was mixed with a second containing both DNA and MgCl2: in these reactions, the fluorescence changed at the same rate as the cleavage of the first strand of the duplex. Other reactions were started by the addition of MgCl2 to a pre-equilibrium of enzyme and DNA: here, both strands of the DNA were cleaved faster than before, with the fluorescence signal now occurring at the same time as the cleavage of the second strand. The different kinetics from the two assays and the two mixing procedures are consistent with the rates of these reactions being controlled by protein conformational changes. These may affect either one subunit alone within the dimeric EcoRI enzyme, allowing the enzyme to cleave only one strand of the DNA in each turnover. Alternatively, both subunits of the dimer may change, so that the enzyme then cleaves both strands during the life-time of one enzyme-DNA complex.
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PMID:Single turnovers of the EcoRI restriction endonuclease. 630 79

Fragments specific for the amplified regions in DNA of Djungarian hamster colchicine-resistant cells were studied after restriction endonuclease digestion. We used three different methods of detection of these fragments: a) comparison of the wild type and resistant cell DNA electroforegramms stained by ethidium bromide; b) blotting of DNA from sensitive and resistant variants onto nitrocellulose filters and their hybridization with nick-translated DNA from resistant cells, in the presence of the excess of unlabelled DNA from the wild type cells (competitive hybridization); c) investigation of autonomously replicating DNA from sensitive and colchicine-resistant sublines. The highest resolution was found using the third method. However, the competitive hybridization is evidently a more universal approach to restriction analysis of DNA amplified sequences, because it gives quite high resolution and may be used for studying both autonomously and non-autonomously replicating sequences.
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PMID:[Amplification of portions of the genome in mammalian somatic cells resistant to colchicine. VI. Restriction analysis of the amplified DNA sequences]. 631 72

The preferred dye binding sites and the microenvironment of known nucleotide sequences within mitochondrial and plasmid pBR322 DNA was probed in a gross fashion with restriction endonucleases. The intercalating dyes, ethidium bromide and propidium iodide, do not inhibit a given restriction endonuclease equally at all of the restriction sites within a DNA molecule. The selective inhibition may be explained, in part, by the potential B to Z conformation transition of DNA flanking the restriction site and by preferred dye binding sites. Propidium iodide was found to be a more potent inhibitor than ethidium bromide and the inhibition is independent of the type of cut made by the enzyme.
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PMID:Selective inhibition of restriction endonuclease cleavage by DNA intercalators. 631 80

We have used topoisomerase I in the presence of netropsin and ethidium bromide to generate DNA molecules of varying superhelical density. Digestion by endonuclease EcoRI is sensitive to supercoiling, being maximal for the relaxed form. Endonucleases AvaI and BamHI, by contrast, are relatively unaffected. The results are interpreted in terms of the base composition of the DNA in the vicinity of these sites. dA + dT-rich regions are more susceptible to deformation than are dG + dC-rich ones. Analysis of the rates of disappearance of linear molecules confirms a two-step mechanism for EcoRI cleavage but suggests that BamHI and AvaI cleave both strands simultaneously.
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PMID:Supercoiling and the mechanism of restriction endonucleases. 632 Nov 70

The genetic nature of penicillin (Pc) and tetracycline (Tc) resistance plasmids in Staphylococcus epidermidis were studied and compared with those in S. aureus. Of 10 S. epidermidis strains transduced for penicillin resistance, we could isolate Pc plasmids from only 3. One of these plasmids also encoded for cadmium resistance and another encoded for resistance to ethidium bromide, traits also associated with S. aureus Pc plasmids. Endonuclease fingerprinting of the Pc plasmids from the two species revealed extensive heterogeneity. Two S. epidermidis strains were also transduced for tetracycline resistance. Both harbored plasmids indistinguishable from S. aureus Tc plasmids as judged by endonuclease fingerprinting. These data suggest that genetic exchange between S. aureus and S. epidermidis occurs in vivo.
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PMID:Penicillin and tetracycline resistance plasmids in Staphylococcus epidermidis. 645 34

Platelets, incubated with radiolabeled thymidine and purified free of contaminating nucleated cells, were analyzed for their ability to synthesize DNA. The only DNA species isolated from these purified platelets was mitochondrial DNA. The CsCl gradient-purified platelet DNA was treated with the restriction endonucleases EcoRI, HindIII and HpaI yielding the expected pattern for human mitochondrial DNA. Nitrocellulose blots of the electrophoresed, restriction endonuclease-treated DNA were fluorographed. All of the DNA fragments generated by the restriction enzymes were labeled, indicating de novo synthesis. This was further substantiated by inhibition of DNA synthesis by ethidium bromide and 2',3'-dideoxythymidine. Platelet DNA appeared to become greatly fragmented after 4 to 7 days storage while all of the thymidine incorporated was observed in intact mitochondrial DNA. These results indicate a continuous degradation of platelet mitochondrial DNA with no apparent repair mechanism. The ability of platelets to synthesize DNA may be associated with the protein synthetic capacity of platelets previously described.
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PMID:De novo synthesis of DNA in human platelets. 663 52

The data on centrifugation of DNA in the density gradient of caesium chloride-ethidium bromide, electron microscopy and electrophoresis of the DNA restricts from the satellite gradient band indicate that Str. antibioticus, the oleandomycin-producing organism possessed extrachromosomal cyclic DNA with the molecular weight of 21.3. 10(6) +/- +/- 0.3 10(6) daltons. The extrachromosomal cyclic DNA had 7 identification sites for endonuclease BamHI, 5 sites for PstI, 12 sites for PvuII, more than 14 sites for SmaI and non for endonucleases Eco RI and HindIII.
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PMID:[Identification and the physicochemical characteristics of the extrachromosomal DNA from a Streptomyces antibioticus strain]. 702 17

The binding of the antibiotic dyes to chromatin fragmented by various ways and to preparations of "complete" (MH3, 206 DNA base pairs) and "minor" MH1, 155 DNA base pairs) nucleosomes was studied. The latter were obtained from the total hydrolysate of nuclear chromatin hydrolysis by Ca-Mg-dependent endonuclease, using preparative electrophoresis in polyacrylamide gel. In liver chromatin of different vertebrate species the actinomycin D binding is decreased by 70% as compared to DNA binding, while that of ethidium bromide is reduced only by 40%. The splitting of part of internucleosomal DNA by Ca-Mg-dependent endonuclease further decreases the number of binding sites for ethidium bromide, but not for actinomycin D. MH3 bid 24 molecules of actinomycin D per 10(3) of nucleotides; their DNA contain 43.4% of GC-pairs. The GC content in MH1 is 47.7%; they bind 28 dye molecules per 10(3) of nucleotides. The data obtained are discussed in terms of possible predominant localization of nucleosomal cores in GC-pair-rich DNA sites.
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PMID:[Probing of the linear distribution of nucleosomes in chromatin]. 709 73

Mitochondrial DNA (mtDNA) was isolated from liver mitochondria of rats between 2 and 24 months of age. The mtDNA was purified by cesium chloride--ethidium bromide isopycnic density gradient centrifugation. In the gradients, in addition to the two expected bands of ethidium--DNA complex, there was observed a third, more dense band (d = 1.69 g/cm3). This novel band, rarely observed in preparations from younger animals, was present in most preparations from older animals. The latter was characterized using the diphenylamine assay(s) and ascertained to contain DNA and carbohydrate components. Agarose gel electrophoresis revealed the DNA of the novel band to have a migration identical to form I mtDNA. Digestion of the novel band with the restriction endonuclease Bam HI yielded products identical to those obtained upon treatment of form I mtDNA with Bam HI. The observation of mtDNA at a density of 1.69 g/cm3 indicates the presence, predominantly in older animals, of a subclass of mtDNA molecules with altered ethidium binding properties. The significance of this mtDNA and its position in the gradient is unclear at this time.
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PMID:Changes in mitochondrial DNA during aging. 716 20


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