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 new type of Escherichia coli mutant which shows increased sensitivity to methyl methane sulfonate but not to UV light or to gamma rays was isolated after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. The mutant is unable to reactivate phage lambdavir or double-stranded phiX174 DNA (replicative form) that had been treated with methyl methane sulfonate. The mutant is sensitive to other alkylating agents, such as ethyl methane sulfonate, mitomycin C, and N-methyl-N'-nitro-N-nitrosoguanidine, as well. It grows normally and exhibits almost normal recombination proficiency. The mutant possesses normal levels of DNA polymerase I, exonuclease I, exonuclease V, endonuclease specific for methyl methane sulfonate-treated DNA, and 3-methyladenine-DNA glycosidase activities. The genetic locus responsible has been named alk and is located near his on the chromosome.
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PMID:Escherichia coli gene that controls sensitivity to alkylating agents. 35 28

Endo-R-HindIII restriction endonuclease fragments obtained from F30 and pMB9 plasmid DNAs were ligated in vitro and used to transform a recB21 recC22 sbcB15 strain of E. coli K-12. The inability of this strain to stably maintain pMB9 alone permitted the isolation of transformants that carried hybrid plasmids containing the sbcB+ allele. These transformants became sensitive to ultraviolet light and recombination defieient and showed a 25-fold increase in the level of exonuclease I activity. The stability of the sbcB hybrid plasmids and their effects on exonuclease I activity have also been determined in wild-type and recA1 genetic backgrounds. The presence of the plasmids results in a 7-fold increase in the level of exonuclease I in a wild-type strain and 15-fold increase in a recA1 strain. The increased activity in the recA1 mutant appears to be a result of increased plasmid stability in this genetic background.
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PMID:Amplification in Escherichia coli of enzymes involved in genetic recombination: construction of hybrid ColE1 plasmids carrying the structural gene for exonuclease I. 79 Mar 87

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

Isolation and general properties of 3'-5' exonucleases I and II (EC 3.1.4.26), which are specific to single-stranded DNA, are described. Such enzymes, being components of replication complexes, could correct replication errors. Homogeneous exonucleases I and II consist of a single subunit with molecular mass of 50 and 40 kDa, respectively. These enzymes are located preferentially in the nuclear membrane and chromatin. They form complexes with nuclear DNA polymerases and some other proteins and are not observed practically in a free state. Molecular masses of the complexes amount from 70 to 1.500 kDa. The complexes dissociate as a result of solution hydrophobization and can be reconstituted after the decrease of hydrophobization. The heavy membrane complex form of 3'----5' exonuclease I manifests enzymatic activities of DNA polymerase alpha (EC 2.7.7.7), non-specific nucleoside triphosphatase (EC 3.1.3.2), nucleotidase (EC 3.1.3.31) and faint activity of endonuclease (EC 3.1.4.5). Complexes under study do not display activity of thymidine kinase (EC 2.7.1.21), marker protein of replitase, neither in G0 nor in S-period.
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PMID:[Homogeneous 3'----5'-exonucleases and their multienzyme complexes from the rat liver]. 234 19

Endonuclease I, exonuclease I, and exonuclease II-deoxyribonucleic acid (DNA) polymerase I activities are not vital functions in Escherichia coli, although the latter two enzymes have been indirectly shown to be involved in DNA repair processes. Acridines such as acridine orange and proflavine interfere with repair in vivo, and we find that such compounds inhibit the in vitro activity of exonuclease I and DNA polymerase I but stimulate endonuclease I activity and hydrolysis of p-nitrophenyl thymidine-5'-phosphate by exonuclease II. Another acridine, 10-methylacridinium chloride, binds strongly to DNA but is relatively inert both in vivo and in vitro. These experiments suggest that acridines affect enzyme activity by interacting with the enzyme directly as well as with DNA. Resulting conformational changes in the DNA-dependent enzymes might explain why similar acridines which form similar DNA complexes have such a wide range of physiological effects. Differential sensitivity of exonuclease I and DNA polymerase I to acridine inhibition relative to other DNA-dependent enzymes may contribute to the acridine sensitivity of DNA repair.
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PMID:Effect of deoxyribonucleic acid ligands on deoxyribonucleases and deoxyribonucleic acid polymerase I of Escherichia coli K-12. 456 96

RecA- mutants of Escherichia coli extensively degrade their DNA following UV irradiation. Most of this degradation is due to the recBC DNase, which suggests that the recA gene is involved in the control of recBC DNase in vivo. We have shown that purified recA protein inhibits the endonuclease and exonuclease activities of recBC DNase on single-stranded DNA. The extent of inhibition is dependent on the relative concentration of recA protein, recBC DNase, and the DNA substrate; inhibition is greatest when the concentrations of DNA and recBC DNase are low and the concentrations of recA protein is high. At fixed concentrations of recA protein and recBC DNase, inhibition is eliminated at high concentrations of DNA. In the presence of adenosine 5'-O-(3-thiotriphosphate), an ATP analog which stabilizes the binding of recA protein to both single- and double-stranded DNA, recA protein is a more potent inhibitor of the nuclease activities on single-stranded DNA and is a weak inhibitor of the exonuclease activity on double-stranded DNA. Inhibition of the latter is enhanced by oligodeoxynucleotides, which stimulate the binding of recA protein to double-stranded DNA. In the presence of adenosine 5'-O-(3-thiotriphosphate), recA protein also inhibits the action of exonuclease I on single-stranded DNA and of lambda exonuclease on double-stranded DNA. These observations are most consistent with the idea that recA protein protects DNA from recBC DNase by binding to DNA. RecA protein also blocks the endonucleolytic cleavage of gapped circular DNA by recBC DNase. Since both recA protein and recBC DNase have the ability under certain conditions to unwind duplex DNA and to displace strands, we looked for evidence that their combined action would enlarge gaps but found no extensive enlargement. D-loops, a putative intermediate in genetic recombination, are effectively protected against the action of recBC DNase by the E. coli single strand binding protein and by recA protein in the presence of adenosine 5'-O-(3-thiotriphosphate).
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PMID:Escherichia coli recA protein protects single-stranded DNA or gapped duplex DNA from degradation by RecBC DNase. 626 52

Employing the recombinant runaway replication plasmid pDPK13 [sbcB+], an exonuclease I-overproducing derivative of Escherichia coli K12 has been constructed. The strain SK4258 has exonuclease I activity 140-400-fold higher than wild type control levels. A new purification procedure has been developed such that the protein can be purified to near homogeneity and is free of endonuclease and RNase activities. The specific activity of the purified enzyme is 10-fold higher than reported previously (Ray, R.K., Reuben, R., Molineux, I., and Gefter, M. (1974) J. Biol. Chem. 249, 5379-5381). Native exonuclease I is a single polypeptide having Mr = 55,000 with a Stokes radius of 3.12 nm.
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PMID:Amplification and purification of exonuclease I from Escherichia coli K12. 634 75

The single-stranded-DNA-binding (SSB) proteins from Proteus mirabilis and Serratia marcescens were purified from overproducing Escherichia coli strains, which were devoid of their own ssb gene. The strains harboured an endA insertion mutation and a xonA mutation resulting in the absence of endonuclease I and exonuclease I activities from the preparations. The amino acid sequences of the SSB of all three species are nearly identical in the N-terminal parts of the proteins that contain the DNA-binding domain, but differ in the C-terminal parts. Both proteins have an apparent binding-site size of 65 and 35 nucleotides at high and low salt concentrations, respectively. The association-rate constant for binding to poly(dT) is 3.2 x 10(8) M-1 s-1 for P. mirabilis SSB (PmiSSB) and 3.4 x 10(8) M-1 s-1 for S. marcescens SSB (SmaSSB). These binding parameters are very similar to those of E. coli SSB (EcoSSB). The structural similarity of the proteins is also documented by the finding that they can exchange subunits among each other to form mixed tetramers. The transcriptional regulation of the ssb and uvrA genes from P. mirabilis and S. marcescens in SOS-induced E. coli cells was studied using lacZ fusions. While the uvrA genes were inducible, there was no induction of the ssb genes transcribed divergently from the uvrA genes. Apparently, regions with nucleotide sequence similarity to the E. coli SOS-box preceding the ssb genes of P. mirabilis and S. marcescens had no gross effect on the transcription. Studies on growth of the cells and recovery from ultraviolet damage indicate that the heterologous SSB proteins support DNA replication and recombinational DNA repair of E. coli with the same efficiency as the E. coli SSB protein. Interactions with other E. coli proteins involved in these processes either do not occur, or are not impeded.
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PMID:The single-stranded-DNA-binding proteins (SSB) of Proteus mirabilis and Serratia marcescens. 792 78

The E. coli single-stranded binding protein (SSB) has been demonstrated in vitro to be involved in a number of replicative, DNA renaturation, and protective functions. It was shown previously that SSB can interact with exonuclease I to stimulate the hydrolysis of single-stranded DNA. We demonstrate here that E. coli SSB can also enhance the DNA deoxyribophosphodiesterase (dRpase) activity of exonuclease I by stimulating the release of 2-deoxyribose-5-phosphate from a DNA substrate containing AP endonuclease-incised AP sites, and the release of 4-hydroxy-2-pentenal-5-phosphate from a DNA substrate containing AP lyase-incised AP sites. E. coli SSB and exonuclease I form a protein complex as demonstrated by Superose 12 gel filtration chromatography. These results suggest that SSB may have an important role in the DNA base excision repair pathway.
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PMID:Escherichia coli single-stranded DNA binding protein stimulates the DNA deoxyribophosphodiesterase activity of exonuclease I. 812 10

Exonuclease I of E. coli is a 3'-->5' exonuclease acting on single-stranded DNA. We further demonstrate that the enzyme can remove phosphoglycolate groups at 3' termini in DNA. These types of lesions are introduced into DNA by agents that cause oxidative damage such as ionizing radiation. An oligonucleotide substrate pd(T)20[32P]dA was treated with acid to remove the adenine base to generate 3' termini containing 2-deoxyribose-5-phosphate end groups. This substrate was then treated with periodate to generate 3'-phosphoglycoaldehyde groups and was further oxidized with I2 to generate 3'-phosphoglycolate groups. The pd(T)20[32P]PGA substrate was annealed to pd(A)40-60 to produce a double-stranded substrate. Exonuclease I was effective in the removal of the 3'-phosphoglycolate groups from this substrate as determined by HPLC separation. With exonuclease III and endonuclease IV of E. coli, exonuclease I is the third activity found in E. coli that is able to excise deoxyribose-phosphate fragments at 3' termini in DNA. These sugar fragments are blocks to DNA polymerase, and their removal is necessary to complete the base excision repair process.
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PMID:Exonuclease I of Escherichia coli removes phosphoglycolate 3'-end groups from DNA. 836 94


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