Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A DNA polymerase from Ustilago maydis has been purified to apparent homogeneity. The native enzyme possesses a subunit structure consisting of 50000 and 55000-dalton monomers. The apparent sedimentation coefficient of the polymerase activity in the absence of salt is 8.4 S (Mr=180000-200000), that in its presence (0.6 M NaCl or 0.12 M KCl) being 6.3 S (Mr=80000-100000). Low concentrations of EDTA also converted the 8.4-S to a 6.3-S form, whereas magnesium ions catalysed the reverse association. The enzyme has an absolute requirement for both a DNA or RNA template and a DNA primer. For homopolymer templates the primer requirement was satisified by a short complementary oligodeoxynucleotide, but oligoribonucleotides were extremely inefficient primers. With the template-primer poly(dA) X (dT)12, the enzyme added an average of 50 dTMP nucleotides on to each primer molecule, whereas with poly(rA) X (dT)12, this figure was 300. The enzyme also possesses an associated deoxyribonuclease activity. No other DNA polymerase activity was detected in cell-free extracts of U. maydis.
 ...
PMID:A DNA polymerase from Ustilago maydis. 1. Purification and properties of the polymerase activity. 124 75

The polymerase and deoxyribonuclease activities of the purified Ustilago maydis DNA polymerase coeluted from a hydroxyapatite column, cosedimented in sucrose gradients in both the absence and presence of salt, possessed similar thermolabilities and reaction requirements. These observations suggest that both activities are associated with the same enzyme and that the deoxyribonuclease activity is not a contaminant. The initial rate of degradation of native 3'-end-group-labelled DNA was similar to that of a heat-denatured substrate, but the final extent was greater for the former. The enzyme exhibits a high specificity for degradation of DNA in a 3' leads to 5' direction. The degradation of a DNA template was inhibited by the presence of the deoxyribonucleoside triphosphates necessary for simultaneous DNA synthesis, but not that of the newly synthesised DNA. About 50%, 29% and 13% of the purine, cytosine and thymine deoxyribonucleotide residues incorporated by the enzyme into DNA respectively, were subsequently excised when monitored by the resulting conversion of the triphosphate substrates to free monophosphate. The majority of the purine deoxyribonucleoside monophosphates appear after the synthetic phase of the reaction has ceased. In many respects, therefore, the deoxyribonuclease activity of the U. maydis DNA polymerase is similar to the bacteriophage T4-induced enzyme.
 ...
PMID:A DNA polymerase from Ustilago maydis. 2. Properties of the associated deoxyribonuclease activity. 124 76

We have purified to homogeneity the primer recognition proteins (PRP) from human HeLa cells. PRP is associated with DNA polymerase alpha complex in HeLa cells. Purified PRP is free of DNA polymerases alpha, beta, and delta, deoxyribonuclease, DNA primase, ATPase, topoisomerase, and DNA ligase activities. The protein structure of the PRP was defined by sodium dodecyl sulfate gel electrophoresis, which revealed two polypeptides of 36,000 Da (PRP 1) and 41,000 Da (PRP 2). The two polypeptides are associated in a complex in the native state. The Stokes radius of the PRP complex by gel filtration is 40.5 A and the sedimentation coefficient in glycerol gradients is 5.7 S. Purified PRP, which exhibits no DNA polymerase activity, completely restores the activity of DNA polymerase alpha on templates with low primer to template ratios such as heat-denaturated DNA, poly(dA)-oligo(dT), and singly primed M13 single-stranded DNA. Experiments using various amounts of PRP, DNA polymerase alpha, and DNA indicate that a concentration dependence exists between these components in the DNA replication process. Amino acid composition analysis indicates that the PRP is rich in hydrophobic amino acids.
 ...
PMID:Purification and characterization of primer recognition proteins from HeLa cells. 236 57

Phosphorylation is a major post-translational regulatory mechanism and plays a key role in transduction of mitogenic signals in cell proliferation. The role of phosphorylation and dephosphorylation in regulating the activities of a multiprotein DNA polymerase alpha complex was examined. Treatment of the HeLa cell multiprotein DNA polymerase alpha with calf intestinal alkaline phosphatase resulted in the inactivation of DNA polymerase alpha and DNA primase but had no effect on deoxyribonuclease- and primer-recognition proteins. A protein kinase co-purified with the multiprotein DNA polymerase alpha and was partially purified from HeLa cells. The partially purified kinase was active in phosphorylating dephosphorylated polymerase alpha and used casein and histones as exogenous substrates. This study demonstrates that phosphorylation-dephosphorylation may have modulated the activities of DNA replicative enzymes and suggests a role for specific phosphatases and kinases in this process.
 ...
PMID:Phosphorylation of HeLa cell multiprotein DNA polymerase alpha complex: impact on activity and partial purification of the associated kinase. 256 5

Exonuclease A was isolated from bacteriophage T4-infected cells of E. coli. The molecular mass of the enzyme is approximately 42,000 Da, pH optimum is 7-8.5, pI is 4.05. The enzyme activity depends on Mg2+, the optimal concentration of Mg2+ being 1-5 mM. The enzyme splits one- and two-helical DNA in the direction of 3'----5' and is a deoxyribonuclease splitting 5'-deoxynucleotides. The enzyme shows a practically equal affinity for one and two-helical DNA. The Km value for one- and two-helical DNA is 10 +/- 1 and 11 +/- 1 pmole of chain DNA, respectively. The Vmax value for one- and two-helical DNA is 61 +/- 5 and 45 +/- 5 pmole of nucleotides per min. Exonuclease A may be used for preparing substrates for DNA-polymerase T4 and Klenow fragment, i.e., during labeling of DNA at 3'-ends.
 ...
PMID:[Purification and various properties of exonuclease from bacteriophage T4]. 303 41

Early chicken embryos that are either positive or negative for group-specific antigens of avian leukosis viruses contained endogenous RNA-directed DNA polymerase activity. This endogenous DNA polymerase activity was not increased after mixture of soluble DNA polymerases isolated from chicken embryos with disrupted chicken embryo cells. The endogenous activity was resistant to treatment with deoxyribonuclease, and the initial rate of DNA synthesis was partially resistant to actinomycin D. In contrast, over 90% of the endogenous polymerase activity was destroyed by ribonuclease in medium with high salt concentration. The DNA product of the endogenous DNA polymerase activity from chicken embryos did not hybridize with RNA of Rous sarcoma virus or reticuloendotheliosis virus, whereas about 40% of this DNA product hybridized with the RNA from the same chicken-cell fraction. Antibody against DNA polymerase of avian myeloblastosis virus did not neutralize the chicken endogenous DNA polymerase activity. These results demonstrate that uninfected chicken embryo cells contain endogenous RNA-directed DNA polymerase activity that is not derived from avian leukosis or reticuloendotheliosis viruses.
 ...
PMID:Endogenous RNA-directed DNA polymerase activity in uninfected chicken embryos. 433 97

Patterns of deoxyribonucleic acid (DNA) metabolism in nonpermissive cells infected with amber mutants representing 29 genes of T5 are reported. A group of 7 contiguous genes are essential for the synthesis of phage DNA, whereas 20 other genes, when defective, permit varying degrees of phage DNA synthesis. Two further genes are essential for complete transfer of phage DNA to host cells, and therefore indirectly do not permit the synthesis of phage DNA. The structural genes for an early T5 deoxyribonuclease and for T5 DNA polymerase, as well as a gene that affects the synthesis of dihydrofolate reductase, have been identified in the genetic map of T5.
 ...
PMID:Genetic and physiological studies of bacteriophage T5. 3. Patterns of deoxyribonucleic acid synthesis induced by mutants of T5 and the identification of genes influencing the appearance of phage-induced dihydrofolate reductase and deoxyribonuclease. 455 11

Amber (am) mutants of the two closely linked sites, B22 and C125, in bacteriophage T4 gene 43 [deoxyribonucleic acid (DNA) polymerase] synthesize in the nonpermissive (su(-)) Escherichia coli host gene 43 products which are devoid of DNA polymerase activity, but which retain a 3'-exonuclease activity. Diethylaminoethyl-cellulose chromatographic analysis of DNA polymerase and deoxyribonuclease activities from extracts of su(-) cells infected with single- and double-am mutants of T4 gene 43 showed that the exonuclease activity which is observed with amB22 is not seen with double mutants carrying, in addition to amB22, am mutations which map to the clockwise side of the B22 site on the circular genetic map of T4. Similarly, am mutations which map to the clockwise side of the C125 site abolish the exonuclease activity which is observed with an am mutant (amE4335) of this site. It was concluded that in these double mutants termination signals to the clockwise side of amB22 and amE4335 are encountered before the amB22 and amE4335 signals during translation of the messenger ribonucleic acid from T4 gene 43. Thus, it seems that the T4 DNA polymerase is synthesized in vivo in a direction which corresponds to a counterclockwise reading of gene 43.
 ...
PMID:On the direction of reading of bacteriophage T4 gene 43 (deoxyribonucleic acid polymerase). 455 12

1. The activities of DNA polymerase preparations from the algae Euglena gracilis, Chlamydomonas reinhardtii, Chlorella pyrenoidosa, Anabaena variabilis and Anacystis nidulans were measured. The blue-green algae Anabaena and Anacystis contain a 5-20-fold higher activity of the enzyme than do the green algae. DNA polymerases from the blue-green algae show a pH optimum of 9 and prefer a relatively low Mg(2+) concentration (1-3mm). DNA polymerases from the green algae, however, display a pH optimum between 7.5 and 8.5 and an optimum Mg(2+) concentration of 8mm. With all algae, a higher polymerase activity was obtained with denatured salmon sperm DNA as template than with native DNA. All four deoxyribonucleoside 5'-triphosphates must be present for full activity of the polymerases. 2. With one exception, the deoxyribonuclease activities in the preparations, measured under conditions of the DNA polymerase assay, are low compared with corresponding preparations from Escherichia coli. Chlamydomonas extracts contain a high deoxyribonuclease activity. 3. After purification on columns of DEAE-cellulose, the polymerase activity was linear over a wide range of protein concentrations, except for Chlamydomonas preparations, where the observed deviation from linearity was probably attributable to the high nuclease activity. 4. DNA polymerases from all these algae bind strongly to DNA-cellulose; 6-40-fold purifications of the enzyme were obtained by chromatography on columns of DNA-cellulose. 5. The partially purified polymerases of Euglena and Anacystis are heat-labile but become much more heat-stable when tested in the presence of DNA.
 ...
PMID:The activity of deoxyribonucleic acid polymerase in some species of algae. 462 75

A number of bacterial species have been surveyed for serological activities with antiserum to Escherichia coli B deoxyribonucleic acid (DNA) polymerase I (EC 2.7.7.7.). The degree of serological cross-reaction is taken as a measure of relatedness of both the enzyme molecules from various species and the bacterial species themselves. Extracts were assayed by complement fixation only after treatment with deoxyribonuclease, since DNA bound to DNA polymerase alters the serological activity of the enzyme. Antiserum to E. coli DNA polymerase I did not react with either purified E. coli DNA polymerase II or the phage T4-induced DNA polymerase.
 ...
PMID:Serological relatedness of bacterial deoxyribonucleic acid polymerases. 463 May 12


<< Previous 1 2 3 4 5 6 Next >>