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)

An endonuclease that makes single polynucleotide chain scissions in ultraviolet-irradiated DNA has been purified from Escherichia coli. The activity has the following properties: (a) unirradiated DNA is attacked very little if at all; (b) single strand DNA is not attacked, whether irradiated or not; (c) there is no requirement for divalent cations and the activity is not affected by the addition of EDTA; (d) the pH optimum is approximately 7; (e) the activity is inhibited by 1 M NaCl, single strand DNA, transfer RNA and double strand DNA; (f) the sedimentation coefficient, S20,w, is approximately 2.6; (g) it is a basic protein. The enzyme is tentatively named E. coli endonuclease III. The physiological function of the endonuclease has not yet been established.
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PMID:An endonuclease from Escherichia coli that introduces single polynucleotide chain scissions in ultraviolet-irradiated DNA. 0 98

An endonuclease which is active upon DNA exposed to ultraviolet light at a photoproduct other than thymine dimers has been extensively purified from Escherichia coli. The small (2.7 S) enzyme is active in the presence of EDTA, has a neutral pH optimum, and is inhibited by tRNA and 1 M NaCl. It has no detectable exonuclease, DNA-N-glycosidase, or ribonuclease activities. The enzyme also nicks duplex DNA exposed to OsO4, x-rays, or acid, but it does not act upon undamaged DNA or irradiated single-stranded DNA. The majority of sites of action in DNA exposed to ultraviolet light or OsO4 appear to be alkali-stable, but those in DNA exposed to x-rays or acid are not. The incisions created by the endonuclease contain 5'-phosphate termini. The enzyme is possibly the same as E. coli endonuclease III described by Radman (Radman, M. (1976) J. Biol. Chem. 251, 1438-1445), but it is distinguishable from the other endodeoxyribonucleases described from that organism.
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PMID:Endonuclease from Escherichia coli that acts specifically upon duplex DNA damaged by ultraviolet light, osmium tetroxide, acid, or x-rays. 1 1

An endonuclease that makes single polynucleotide chain scissions in UV-irradiated DNA has been purified from Escherichia coli. The activity has the following properties: (1) unirradiated DNA is attacked very little if at all; (2) single-stranded DNA is not attacked, whether irradiated or not; (3) there is no requirement for divalent cations, and the activity is not affected by addition of EDTA; (4) the pH optimum is approximately 7; (5) the activity is inhibited by 1 M NaCl, single-stranded DNA, transfer RNA, and unirradiated double-stranded DNA; (6) the sedimentation coefficient, S20, W, is approximately 2.6; (7) it is a basic protein. The enzyme is tentatively named E. coli endonuclease III. The physiological function of the endonuclease has not yet been established.
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PMID:Endonuclease III: an endonuclease from Escherichia coli that introduces single polynucleotide chain scissions in ultraviolet-irradiated DNA. 24 12

DNA deoxyribophosphodiesterase (dRpase) of E. coli catalyzes the release of deoxyribose-phosphate moieties following the cleavage of DNA at an apurinic/apyrimidinic (AP) site by either an AP endonuclease or AP lyase. Exonuclease I is a single-strand specific DNA nuclease which affects the expression of recombination and repair pathways in E. coli. We show here that a major dRpase activity in E. coli is associated with the exonuclease I protein. Highly purified exonuclease I isolated from an over-producing stain contains high levels of dRpase activity; it catalyzes the release of deoxyribose-5-phosphate from an AP site incised with endonuclease IV of E. coli and the release of 4-hydroxy-2-pentenal-5-phosphate from an AP site incised by the AP lyase activity of endonuclease III of E. coli. A strain containing a deletion of the sbcB gene showed little dRpase activity; the activity could be restored by transformation of the strain with a plasmid containing the sbcB gene. The dRpase activity isolated from an overproducing stain was increased 70-fold as compared to a normal sbcB+ strain (AB3027). These results suggest that the dRpase activity may be important in pathways for both DNA repair and recombination.
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PMID:DNA deoxyribophosphodiesterase of Escherichia coli is associated with exonuclease I. 132 27

It has been shown previously that the DNA deoxyribophosphodiesterase (dRpase) activity of Escherichia coli excises 2-deoxyribose 5-phosphate moieties at apurinic/apyrimidinic (AP) sites in DNA following cleavage of the DNA at the AP site by an AP endonuclease such as endonuclease IV of E coli. A second class of enzymes that cleave DNA at AP sites by a beta-elimination mechanism, AP lyases, leave a different sugar-phosphate product remaining at the AP site, which has been identified as the compound trans-4-hydroxy-2-pentenal 5-phosphate. It is shown that dRpase removes this unsaturated sugar-phosphate group following cleavage of a poly(dA-dT) substrate containing AP sites by the action of the AP lyase endonuclease III of E. coli. The Km for the removal of trans-4-hydroxy-2-pentenal 5-phosphate is 0.06 microM; the Km for the removal of 2-deoxyribose 5-phosphate is 0.17 microM. It was verified that the sugar-phosphate product removed by dRpase from the endonuclease III-cleaved substrate was trans-4-hydroxy-2-pentenal 5-phosphate by conversion of the product to the compound cyclopentane-1,2-dione. The dRpase activity is unique in its ability to remove sugar-phosphate products after cleavage by both AP endonucleases and AP lyases.
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PMID:Excision of sugar-phosphate products at apurinic/apyrimidinic sites by DNA deoxyribophosphodiesterase of Escherichia coli. 133 11

Unlike its phage T4 counterpart (also known as endonuclease V), Micrococcus luteus UV endonuclease (pyrimidine dimer DNA glycosylase/apurinic-apyrimidinic endonuclease) has suffered from lack of genetic evidence to implicate it in the promotion of UV survival of the cell, i.e., mutants with its deficiency are no more UV-sensitive than the wild type. On the assumption that the contribution of UV endonuclease is obscured by the presence of a homolog of Escherichia coli UvrABC endonuclease, which has recently been identified in this bacterium, survival studies were carried out in its absence. With 254-nm UV irradiation, which generates not only pyrimidine dimers but also 6-4 photoproducts as lethal lesions, a double mutant defective in both UV endonuclease and the Uvr homolog was shown to be more sensitive than a single mutant defective only in the latter, with a dose reduction factor of approximately 2 at the survival level of 37%. Furthermore, molecular photosensitization, which produces only pyrimidine dimers, revealed an even greater difference in sensitivity, the dose reduction factor being about 3.4. These results indicate that the contribution to cell survival of UV endonuclease, an enzyme specific for pyrimidine dimers, is manifest if the backup by the Uvr homolog is absent.
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PMID:UV endonuclease-mediated enhancement of UV survival in Micrococcus luteus: evidence revealed by deficiency in the Uvr homolog. 137 34

Thioglycollate reacts with the 5' product of AP lyase activity on apurinic/apyrimidinic (AP) sites in DNA. The 3'-terminal thioglycollate-unsaturated sugar 5-phosphate adduct can be released by the use of Escherichia coli endonuclease IV or endonuclease VI, and identified by DEAE-Sephadex chromatography. In contrast, the mammalian AP endonuclease is unable to excise a 3'-terminal thiol-unsaturated sugar adduct; this lesion, which must sometimes occur in vivo, might be irreparable and have pathological consequences.
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PMID:The use of thioglycollate to demonstrate DNA AP (apurinic/apyrimidinic-site) lyase activities. Biological consequences of thiol addition to the 5' product of a beta-elimination reaction at an AP site in DNA. 170 16

In this study we demonstrate that the different substrate recognition properties of bacterial and human AP endonucleases might be used to quantify and localize apurinic (AP) sites formed in DNA in vivo. By using a model oligonucleotide containing a single AP site modified with methoxyamine (MX), we show that endonuclease III and IV of E. coli are able to cleave the alkoxyamine-adducted site whereas a partially purified HeLa AP endonuclease and crude cell-free extracts from HeLa cells are inhibited by this modification. In addition MX-modified AP sites in a DNA template retain their ability to block DNA synthesis in vitro. Since MX can efficiently react with AP sites formed in mammalian cells in vivo we propose that the MX modified abasic sites thus formed can be quantitated and localized at the level of the individual gene by subsequent site specific cleavage by either E. coli endonuclease III or IV in vitro.
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PMID:Processing in vitro of an abasic site reacted with methoxyamine: a new assay for the detection of abasic sites formed in vivo. 171 78

The mechanism of action of a DNA repair endonuclease isolated from calf thymus was determined. The calf thymus endonuclease possesses a substrate specificity nearly identical with that of Escherichia coli endonuclease III following DNA damage by high doses of UV light, osmium tetroxide, and other oxidizing agents. The calf thymus enzyme incises damaged DNA at sites of pyrimidines. A cytosine photoproduct was found to be the primary monobasic UV adduct. The calf thymus endonuclease and E. coli endonuclease III were found to possess similar, but not identical, DNA incision mechanisms. The mechanism of action of the calf thymus endonuclease was deduced by analysis of the 3' and 5' termini of the enzyme-generated DNA scission products with DNA sequencing methodologies and HPLC analysis of the material released by the enzyme following DNA damage. The calf thymus endonuclease removes UV light and osmium tetroxide damaged bases via an N-glycosylase activity followed by a 3' apurinic/apyrimidinic (AP) endonuclease activity. The calf thymus endonuclease also possesses a novel 5' AP endonuclease activity not possessed by endonuclease III. The product of this three-step mechanism is a nucleoside-free site flanked by 3'-and 5'-terminal phosphate groups. These results indicate the conservation of both substrate specificity and mechanism of action in the enzymatic removal of oxidative base damage between prokaryotes and eukaryotes. We propose the name redoxy endonucleases for this group of enzymes.
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PMID:Mechanism of action of a mammalian DNA repair endonuclease. 242 22

The oligonucleotide [5'-32P]pdT8d(-)dTn, containing an apurinic/apyrimidinic (AP) site [d(-)], yields three radioactive products when incubated at alkaline pH: two of them, forming a doublet approximately at the level of pdT8dA when analysed by polyacrylamide-gel electrophoresis, are the result of the beta-elimination reaction, whereas the third is pdT8p resulting from beta delta-elimination. The incubation of [5'-32P]pdT8d(-)dTn, hybridized with poly(dA), with E. coli endonuclease III yields two radioactive products which have the same electrophoretic behaviour as the doublet obtained by alkaline beta-elimination. The oligonucleotide pdT8d(-) is degraded by the 3'-5' exonuclease activity of T4 DNA polymerase as well as pdT8dA, showing that a base-free deoxyribose at the 3' end is not an obstacle for this activity. The radioactive products from [5'-32P]pdT8d(-)dTn cleaved by alkaline beta-elimination or by E. coli endonuclease III are not degraded by the 3'-5' exonuclease activity of T4 DNA polymerase. When DNA containing AP sites labelled with 32P 5' to the base-free deoxyribose labelled with 3H in the 1' and 2' positions is degraded by E. coli endonuclease VI (exonuclease III) and snake venom phosphodiesterase, the two radionuclides are found exclusively in deoxyribose 5-phosphate and the 3H/32P ratio in this sugar phosphate is the same as in the substrate DNA. When DNA containing these doubly-labelled AP sites is degraded by alkaline treatment or with Lys-Trp-Lys, followed by E. coli endonuclease VI (exonuclease III), some 3H is found in a volatile compound (probably 3H2O) whereas the 3H/32P ratio is decreased in the resulting sugar phosphate which has a chromatographic behaviour different from that of deoxyribose 5-phosphate. Treatment of the DNA containing doubly-labelled AP sites with E. coli endonuclease III, then with E. coli endonuclease VI (exonuclease III), also results in the loss of 3H and the formation of a sugar phosphate with a lower 3H/32P ratio that behaves chromatographically as the beta-elimination product digested with E. coli endonuclease VI (exonuclease III). From these data, we conclude that E. coli endonuclease III cleaves the phosphodiester bond 3' to the AP site, but that the cleavage is not a hydrolysis leaving a base-free deoxyribose at the 3' end as it has been so far assumed. The cleavage might be the result of a beta-elimination analogous to the one produced by an alkaline pH or Lys-Trp-Lys. Thus it would seem that E. coli 'endonuclease III' is, after all, not an endonuclease.
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PMID:Escherichia coli endonuclease III is not an endonuclease but a beta-elimination catalyst. 243 70


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