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)

The presence of endonuclease activity associated with DNA polymerase was detected during the purification of high-molecular-weight DNA polymerase-alpha from regenerating rat liver by the use of a highly sensitive test. This endonuclease activity co-fractionated with DNA polymerase in a great variety of purification procedures involving ion-exchange chromatographies or molecular weight fractionation, but was further completely separated from DNA polymerase activity by using affinity chromatography on DNA-cellulose. The endonuclease acted on native or denatured DNA by introducing single-strand nicks in the DNA molecules; its enzymatic properties indicate that it could act in polymerisation conditions in vitro.
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PMID:Co-fractionation of an endonuclease activity during the purification of DNA polymerase-alpha from regenerating rat liver. Properties and separation from DNA polymerase. 24 42

DNA polymerase-alpha and -beta can be distinguished from one another by the differential effects of N-ethylmaleimide, KCl, ara-CTP and temperature, as well as on the basis of sedimentation. The sensitivity of DNA polymerase-beta to elevated temperatures as compared to DNA polymerase-alpha provides a new means of distinguishing between these two enzymes even in crude extracts and a possible probe for determining their function. DNA polymerase-alpha and -beta share several properties in common, including the ability to readily incorporate dUTP in place of dTTP. The Km for dUTP varies from 10 to 30 micron with different preparations of DNA polymerase-alpha and -beta. Thus, in mammalian cells, dUMP could be incorporated into DNA, and if excised by an endonuclease, would lead to discontinuities. Initial analyses of fidelity in direct comparative studies indicate that beta-class DNA polymerases are highly accurate in base selection when copying poly[d(A-T)]. Less than one molecule of dGMP is incorporated for every 12 000-45 000 molecules of dAMP and dTMP polymerized. DNA polymerase-alpha is somewhat less accurate, making one mistake for every 4000-10 000 correct nucleotides incorporated. Since both polymerases lack an exonucleolytic activity, this accuracy must be the result of selectivity for the complementary nucleotide by the polymerase.
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PMID:Distinctive properties of mammalian DNA polymerases. 28 7

DNA polymerase-alpha from the cytosol of regenerating rat liver has been highly purified by a procedure which includes affinity chromatography. The purified enzyme sediments at 7.4 S in high ionic strength and at 9--10 S in low ionic strength, i.e. under in vitro polymerization conditions. This enzyme has all the properties of the other mammalian DNA polymerases-alpha: sensitivity to sulfhydryl-blocking agents, to heparin, and to the level of salt in the assay, neutral pH optimum, use of ribonucleotide-initiated DNA templates, and inability to copy the ribostrand of hybrids. After chromatography on denatured DNA-cellulose, the alpha-polymerase is completely devoid of exo- and endonuclease activities. Template competition experiments indicate that the binding of the enzyme to the template can be distinguished from the polymerization itself and that the in vitro synthesis catalyzed by this alpha-polymerase is not distributive in a classical sense. These facts are discussed.
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PMID:DNA polymerase-alpha from regenerating rat liver. Catalytic properties of the highly purified enzyme. 42 Aug 53

A synthetic procedure has been developed by which stable abasic sites are introduced into oligodeoxynucleotides at any desired position in the sequence. A modified tetrahydrofuran moiety, isosteric with 2'-deoxyribofuranose, serves as a structural analog of the natural apurinic/apyrimidinic site. We have also prepared oligodeoxynucleotides that lack cyclic structure at the abasic site but retain the carbon atoms of the phosphodiester backbone. These synthetic oligodeoxynucleotides are cleaved on the 5' side of the abasic site by endonuclease IV and by exonuclease III; they serve also as templates for avian myeloblastosis virus reverse transcriptase, Escherichia coli DNA polymerase I (Klenow fragment), and calf thymus DNA polymerase-alpha. Extension of primed templates by these DNA polymerases is blocked initially at the position immediately 3' to the abasic site; nucleoside monophosphates are subsequently incorporated opposite the lesion. The nucleotide most frequently incorporated opposite all abasic sites, regardless of structure, is dAMP. Significant "readthrough" at the abasic site was observed in experiments using avian myeloblastosis virus reverse transcriptase and DNA polymerase-alpha and, to a much lesser degree, with DNA polymerase I. We conclude that a modified tetrahydrofuran group can serve as a stable structural analog of 2'-deoxyribose in the apurinic/apyrimidinic site. These modified oligodeoxynucleotides should prove useful for studies of chemical mutagenesis.
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PMID:Oligodeoxynucleotides containing synthetic abasic sites. Model substrates for DNA polymerases and apurinic/apyrimidinic endonucleases. 244 Aug 61