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:2.7.7.7 (DNA polymerase)
17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

For the first time, DNA polymerase in a postembryonic insect has been purified and characterized. This enzyme from mosquito larvae was purified 1700-fold and was free of deoxyribonuclease and protease activities, which hindered previous investigations of insect polymerases. The enzyme had a molecular weight of 132,000 by gen filtration and aggregated to higher molecular weights when concentrated. With an activated DNA template, the pH optimum was 7.2 in phosphate buffer, and the Mg2+ concentration optimum was 5 to 10 mM. Polymerase activity was inhibited by the antisulfhydryl reagents, N-ethylmaleimide and p-mercuribenzoate, and by KCl. These properties indicate that the mosquito enzyme resembles mammalian alpha-polymerase but differs in its lack of inhibition to low ethanol concentrations. There was no evidence of a beta-polymerase form in the mosquito.
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PMID:Purification and properties of mosquito DNA polymerase. 2 32

Three DNA polymerase activities, A, B and C, were identified in extracts of exponentially growing synchronous cultures of Chlamydomonas reinhardii, and DNA polymerases A and B were characterized in detail. Both enzymes have the same binding affinity for DEAE-cellulose at pH 7.8, but can be distinguished from each other by their behaviour on phosphocellulose and DNA-agarose. 'Activated' calf thymus DNA was used as template, and the pH, K+ and bivalent-cation optima were measured. DNA polymerase A sediments at 5.3 S in glycerol gradients, with an apparent mol.wt. of 90000-100000. Polymerase B sediments between 8S and 10S in 100mM-KCl, the predominant species having an apparent mol.wt. of 200000. In 200mM-KCl, polymerase B dissociates to a single species, which sediments at 5.8S. A 3S species was found in aged preparations of both enzymes. The activity of polymerase B from cells harvested during nuclear DNA synthesis is twice that found in Chlamydomonas at other times during the cell cycle.
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PMID:DNA polymerases from Chlamydomonas reinhardii. Purification and properties. 2 59

DNA, complementary to chicken globin mRNA was synthesized using either Avian Myeloblastosis virus reverse transcriptase, or E. coli DNA polymerase I. Transcriptase cDNA sediments at 9 S on sucrose gradients, and is 620 nucleotides in length, representing a complete copy of globin mRNA template. In contrast, Polymerase I cDNA sediments at 4 S, is 100 to 200 nucleotides in length, and is a copy of a small region at the 3'(poly A) end of globin mRNA. Similarly, Transcriptase cDNA and Polymerase I cDNA hybridize to globin mRNA template with characteristic, individual Crot1/2 values. The Crot1/2 value for Transcriptase cDNA hybridization is 7 X 10(-4) mol s 1(-1), and that for Polymerase I cDNA is 5 X 10(-3). This work shows that Avian Myeloblastosis virus reverse transcriptase can use Polymerase I cDNA to prime further cDNA synthesis along the mRNA template. The product of extended cDNA synthesis is identical in length and hybridization properties to oligo (dT) primed transcriptase cDNA.
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PMID:Gene specific priming of complementary DNA synthesis. 6 22

A new form of high molecular weight DNA polymerase [EC 2.7.7.7] (polymerase N) was isolated from the nuclei of rat ascites hepatoma cells. Polymerase C, which was isolated previously from whole cell extract, was also isolated from the nuclei (Tsuruo, T. and Ukita, T. (1974) Biochim. Biophys. Acta 353, 146-159). Polymerase N was not found in the cytoplasmic fraction of the cell, while polymerase C existed in both the nucleus and cytoplasm. The molecular weight of polymerase N (8.7 S) was larger than that of polymerase C (7.4 S). On freezing and thawing, polymerase N was converted to polymerase C. In the nucleus the amount of polymerase N was larger than that of polymerase C. These data suggest that polymerase N, which was specifically present in the nucleus, was a complex form of polymerase C. In in vitro assay, polymerase N showed properties similar to those of polymerase C. Oligoribonucleotide was an effective initiator for the polymerization reaction by polymerase N. The DNA synthesis on single stranded fd phage DNA was greatly stimulated by the concomitant synthesis of RNA.
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PMID:A new form of high molecular weight DNA polymerase in the nuclei of rat ascites hepatoma cells. 17 84

Four DNA polymerases from the marine diatom Cylindrotheca fusiformis, polymerases A, B, C and D, were further differentiated by their subcellular localization, presence of deoxyribonuclease activity, apparent heterogeneity and molecular weights. Polymerases A, B and D occur in significant amounts in the soluble fraction, suggesting that they were originally localized in the nuclei, whereas polymerase C predominates in the chloroplasts. A mitochondrial DNA polymerase was also isolated and characterized by ion-exchange chromatography. Polymerase D has an associated nuclease activity which prefers denatured DNA and Mg2+, and has a pH optimum higher than that for polymerase activity. Co-elution from a DEAE-Sephadex column and co-sedimentation in glycerol density gradients of deoxyribonuclease and polymerase D activity suggest a molecular association. Polymerases A, B and C are devoid of nuclease activity. Glycerol-gradient-sedimentation analysis showed that all DNA polymerase fractions are heterogeneous at low ionic strengths, with the appearance of a single homogeneous activity of 0.5M-KCl. Estimated molecular weights of 100000, 82000 and 120000 for polymerases A, B and C respectively were obtained from sedimentation analysis and gel filtration. Polymerase D was estimated to have a molecular weight of about 100000 as determined by sedimentation analysis alone.
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PMID:The deoxyribonucleic acid polymerases from the diatom Cylindrotheca fusiformis. Subcellular distribution, exonuclease activity and heterogeneity of the enzymes. 60 24

DNA polymerase induced by bacteriophage T5 was purified and characterized using mainly circular duplex DNA of bacteriophage PM2 with single strand breaks formed by DNase I action. A purification procedure is described which has consistently yielded DNA polymerase preparations with only one detectable protein band after polyacrylamide gel electrophoresis of either native protein in Tris-glyase preparations utilized both denatured DNA and nicked DNA as primer-templates, although at 37 degrees the activity with denatured DNA was much greater. Polymerase activities with both kinds of primer-templates were shown to be associated with one phage-induced protein. DNA synthesis with nicked DNA as primer-template increased with increasing numbers of single strand breaks. Essentially all such breaks were repairable by ligase. Alkaline sucrose gradient centrifugation showed that synthesis occurred with the strand which had a single strand break as a primer yielding DNA longer than one phage DNA unit length. Newly synthesized DNA was covalently linked to the primer strand. Thus the synthesis very likely occurred by strand displacement; this is supported by electron micrographs shown in the Appendix.
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PMID:Characterization of DNA polymerase induced by bacteriophage T5 with DNA containing single strand breaks. 77 33

Avian erythroid cells were separated into five developmental stages by sedimentation on discontinuous isotonic albumin gradients. Solubilized enzyme activities from whole cells were partially purified and characterized by ion exchange and ion filtration chromatography and velocity sedimenttation analysis. Three nucleotide polymerase types were investigated: (a) DNA-dependent RNA polymerases; (b) RNA-dependent terminal ribonucleotidyltransferases, and (c) DNA-dependent DNA polymerases. The two characteristic forms of eucaryotic DNA-dependent RNA polymerases, polymerase I (nucleolar) and polymerase II (nucleoplasmic), were identified. Polymerase III was only marginally detectable even in the earliest developmental populations. At least two species of RNA-dependent terminal ribosyltransferases were present. One apparently was the poly(A) polymerase observed in other systems. The other terminal transferase was present in two chromatographic forms, required an RNA primer, and used UTP and/or CTP as particularly efficient substrates. Three DNA polymerase activities were resolved, two of which were characteristic of the alpha and beta DNA polymerases described in other eucaryotic systems. The third polymerase was not the gamma polymerase but a separate entity. Poly(dC)-dependent RNA polymerase activity, associated with the alpha polymerase, was relatively enriched in the third DNA polymerase species. The activity levels of the nucleotide polymerases were monitored as a function of red cell maturation. Characteristic declining patterns of activity were obtained for each enzyme which correlate well with the synthetic rates of their in vivo products where these are known. These results correlate well with the synthetic rates of their in vivo products where these are known. These results are consistent with the postulate that the general transcriptive and replicative control processes operating during development may involve changes in the level of the requisite polymerases.
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PMID:Nucleotide polymerases in the developing avian erythrocyte. 83 21

To determine the relation between the presence of donor DNA polymerase and e antigen, and recipient hepatitis, we tested, under code, serums from a controlled trial of hepatitis B immune globulin used to treat individuals accidentally inoculated with HBs Ag-positive blood. All recipients lacked antibody to HBs Ag. In 29 of 31 donors, both polymerase and e were in perfect agreement; both demonstrated a highly significant correlation with recipient hepatitis (P less than 0.001). DNA polymerase/e-negative blood did not cause hepatitis. Blood containing polymerase or e antigen did not cause hepatitis in six of 31 and four of 18 recipients, respectively. Hepatitis did not correlate with transaminase or duration of antigenemia in the donor. Polymerase and e appear to be indicators of the relative infectivity of HBs Ag-positive serum, particularly after small-volume exposure. They may be important determinants in assessing infectivity of chronic carriers of HBs Ag and in evaluating efficacy of hepatitis B immune globulin and hepatitis B vaccines.
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PMID:Type B hepatitis: the infectivity of blood positive for e antigen and DNA polymerase after accidental needlestick exposure. 96

During thymine starvation, strand breaks accumulate in the chromosomal deoxyribonucleic acid (DNA) of Escherichia coli. This effect occurs to a varying extent in different strains and is particularly enhanced in strains deficient in DNA polymerase I. The inhibition of ribonucleic acid or protein synthesis suppresses the accumulation of strand breaks. In a polA strain, rifampin is more effective than chloramphenicol or puromycin in suppressing strand break accumulation. To a certain extent the pehenomenon othymineless death correlates with the appearance of strand breaks. Although the killing can not be explained by the bulk of strand breaks, it is possible that some of them represent lethal events. On the basis of our observations we proposed the following model. (i) Transcription may be accompanied by single-strand breaks in DNA. (ii) DNA polymerase I is involved in the efficient repair of these breaks. (iii) Thymine deprivation results in the accumulation of unrepaired breaks. (iv) Polymerase I-mediated repair is less affected by thymine deprivation than are the alternative pathways because it closes the breaks with short patches, requiring less thymine.
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PMID:Sedimentation analysis of deoxyribonucleic acid from thymine-starved Escherichia coli. 109 May 81

The silk gland of Bombyx mori is a terminally differentiated tissue in which DNA replication continues without cell or nuclear division during larval development. DNA polymerase-delta activity increases in the posterior and middle silk glands during the development period, reaching maximal levels in the middle of the fifth instar larvae. The enzyme has been purified to homogeneity by a series of column chromatographic and affinity purification steps. It is a multimer comprising of three heterogeneous subunits, M(r) 170,000, 70,000, and 42,000. An auxiliary protein from B. mori silk glands, analogous to the proliferating cell nuclear antigen, enhances the processivity of the enzyme and stimulates catalytic activity by 3-fold. This auxiliary protein has also been purified to homogeneity. It is a dimer comprised of a single type M(r) 40,000 subunit. Polymerase-delta possesses an intrinsic 3'----5' exonuclease activity which participates in proofreading by mismatch repair during DNA synthesis and is devoid of any primase activity. DNA polymerase-delta activity could be further distinguished from polymerase-alpha from the same tissue based on its sensitivity to various inhibitors and polyclonal antibodies to the individual enzymes. Like DNA polymerase-alpha, polymerase-delta is also tightly associated with the nuclear matrix. The polymerase alpha-primase complex could be readily separated from polymerase-delta (exonuclease) in the purification protocol adopted. DNA polymerase-delta from B. mori silk glands resembles the mammalian delta-polymerases. Considering that both DNA polymerase-delta and -alpha are present in nearly equal amounts in this highly replicative tissue and their close association with the nuclear matrix, the involvement of both the enzymes in the chromosomal endoreplication process in B. mori is strongly implicated.
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PMID:DNA polymerase-delta from the silk glands of Bombyx mori. 132 38


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