Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several properties of an RNA-directed DNA polymerase associated with a hamster retrovirus (HaRV) were examined and found to be similar to other polymerases from mammalian type-C viruses in that the enzyme (i) is more active with Mn2+ than Mg2+, (ii) uses the reverse transcriptase-specific poly(rCm).oligo(dG) template, (iii) possesses substantial endogenous polymerase activity and (iv) is strongly inhibited by homologous antisera and moderately inhibited by antisera directed against other type-C viruses. In contrast to previous reports of polymerases from other hamster viruses, HaRV polymerase is active in endogenous assays and the activity is associated with a 70,000 mol. wt. polypeptide in highly purified virions and with 70,000 and 85,000 mol. wt. polypeptides in fresh, unpurified virus. Only one major peak of polymerase activity eluted from DEAE-cellulose while subsequent elution of this peak from phosphocellulose produced two major peaks of polymerase activity. The mol. wt. of these two peaks were 70,000 and 85,000 by glycerol density-gradient sedimentation. The HaRV reverse transcriptase and p30 were found to be most closely related antigenically to other rodent retrovirus proteins.
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PMID:Biochemical and immunological properties of the reverse transcriptase associated with a hamster retrovirus. 9 Jan 13

Studies are described on the interrelationships between divalent metals, dNTP's and PPi in determining the properties of complementary DNA (cDNA) product from the in vitro reverse transcriptase reaction with detergent-treated Moloney murine leukemia virus. In spite of the several-fold greater amount of cDNA product with Mn2+ than with Mg2+, net yield of high-molecular-weight cDNA was much greater with Mg2+ thant with Mn2+. This held true, as well, for the reactions containing excess dNTP or dNTP plus PPi, both of which (as has been reported for Mg2+) promote synthesis of high-molecular-weight cDNA product. Hif total dNTP concentration remained important for maximum high-molecular-weight product with Mg2+ and was not replaced by simply providing dNTP in excess over Mg2+. Under the conditions tested here, addition of PPi did not further increase cDNA product size with Mg2+ when compared with dNTP in excess over Mg2+. Extent of degradation of the RNA template during the incubations was correlated with the size of cDNA product.
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PMID:Optimal conditions for synthesis of long complementary DNA product with Moloney murine leukemia virus. 9 Jan 69

Studied were the conditions of cultivation of FLK cells chronically infected with a calf leucosis virus. The gradient values of density were compared to those of the murine sarcoma virus--1.14--1.15 vs, 1.17--1.18/cm3. Established were the parameters of the reverse transcriptase reaction for the calf leukosis virus (Magnesium-dependent reverse transcriptase). Data showed that the calf leucosis virus may not resolutely be referred either to the B- or the the C-type of retroviruses.
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PMID:[Biochemical characteristics of a calf leukemia virus in chronically infected cells]. 9 95

A RNA-dependent DNA polymerase (RTase) was purified from human osteosarcoma tissue by successive column chromatography of the microsomal fraction on DEAE-cellulose (DE-23 and DE-52) and phosphocellulose. The purified enzyme has a molecular weight of about 68,000, a pH optimum of 8.1, a Mg2+ optimum of 0.8 mM, Mn2+ optimum of 1.0 mM and a KCl optimum of 60 mM. The enzyme transcribes (rA)n . (dT)12, (rC)n . (dG)12-18 and (2-O-methyl C)n . (dG)18, but is unable to transcribe (dA)n . (dT)10. The enzyme has no catalytic activity in the presence of oligodeoxynucleotide initiators alone, indicating the absence of terminal deoxynucleotidyl transferase. The purified enzyme is able to transcribe the heteropolymeric regions of a 70S RNA from R(Mu)LV. The presented data support the presence of a RNA-dependent DNA polymerase in human osteosarcoma tissue with biochemical properties, resembling those of C-type RNA tumor viruses.
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PMID:Purification and biochemical characterization of a virus-specific reverse transcriptase from human osteosarcoma tissue. 9 60

The new antiviral substance phosphonoformate (PFA) has been tested in a cell-free system for its effect on reverse transcriptases from an avian retrovirus (avian myeloblastosis virus, AMV) and from mammalian retroviruses (Rauscher leukaemia virus, RMuLV; bovine leukaemia virus; baboon endogenous virus; simian sarcoma virus; visna virus). The observed inhibitory effect of PFA has been compared with that of a structurally related substance, phosphonoacetate (PAA). Phosphonoformate, at a concentration of 100 microM, reduced the activities of all the above mentioned polymerases by 90% when (rA)n.(dT)10 was used as a template/primer. The dose-response curves for AMV and RMuLV polymerases primed with (rA)n.(dT)10 showed PFA to be a 1000-fold more active than PAA; the RMuLV polymerase activity was reduced to 50% after incubation with 0.7 microM-PFA and 0.7 mM-PAA, respectively. There was no difference in PFA inhibition of virus-associated and purified reverse transcriptase activity. Results with various synthetic templates showed that both the RNA- and the DNA-dependent polymerase activities of reverse transcriptase were inhibited by PFA. The endogenous polymerase activity of AMV was inhibited to 50% at 100 microM-PFA, while PAA had no effect. The PFA inhibition was dependent on whether Mg2+ or Mn2+ was used as divalent cation in the assay. Phosphonoformate arrested DNA synthesis immediately after being added to the assay system. The mechanism of inhibition of the AMV polymerase was non-competitive with respect to substrate and template and the apparent inhibition constants were 16 microM and 9 microM, respectively.
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PMID:Phosphonoformate inhibits reverse transcriptase. 9 44

A DNA endonuclease, Endo-I, which cleaves superhelical DNAs, has been isolated from avian myeloblastosis virions stripped of their coats by mild detergent treatment. The enzyme has a broad pH optimum around 7.5-8.0 and requires Mg2+ for activity. A second endonuclease, Endo-II, with a requirement for Mn2+, also present in viral cores, copurified with avian myeloblastosis virus alpha beta DNA polymerase (reverse transcriptase, RNA-dependent DNA nucleotidyltransferase) and similarly cleaved superhelical DNAs. Heat denaturation and sodium fluoride and N-ethylmaleimide inhibition studies were carried out to demonstrate a possible relationship between the two endonucleases and the viral DNA polymerase and RNase H activities. It appears that Endo-II may be an intrinsic activity of the polymerase.
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PMID:DNA endonucleases associated with the avian myeloblastosis virus DNA polymerase. 22 53

Electron microscopic examination of mink lung cells previously cultured with a squirrel monkey (Saimiri sciureus) throat swab suspension revealed the presence of squirrel monkey retrovirus (SMRV) and Herpesvirus saimiri (HVS) coexisting within the same cells in culture. HVS was identified by serum neutralization, and the retrovirus isolate was identified as SMRV by a morphologic examination, microimmunodiffusion analysis, and demonstration of an Mg2+ preference for the RNA-directed DNA polymerase.
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PMID:Squirrel monkey retrovirus and Herpesvirus saimiri: observation in the same cell following isolation. 22 4

An RNA-directed DNA polymerase was purified from bovine leukemia virus (BLV) by successive glycerol gradient centrifugation, column chromatography on phosphocellulose and gel filtration on Sephadex G-200. The purified DNA polymerase transcribes heteropolymeric regions of 30--40 S RNA isolated from avian myeloblastosis virus. The enzyme differs from other known DNA polymerases of mammalian type-C RNA tumor viruses by the following properties: 1. Its apparent molecular weight as estimated by velocity sedimentation data is 58,000 at 0.12 M KCl and 43,000 in the presence of 0.50 M KCl. 2. It has a Mg2+ optimum of 10 mM, and a Mn2+ optimum of 0.25 mM with (rA)n-(dT)10 as template. 3. At 50 mM KCl it is inhibited more than 70%, but it is not inhibited by phosphate ions at 2 mM. These properties confirm the peculiar position of BLV within the family Retraviridae.
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PMID:Purification and characterization of bovine leukemia virus DNA polymerase. 23 43

Purified yeast DNA was transcribed by homologous RNA polymerases I and II and Escherichia coli RNA polymerase. Transcripts synthesized in vitro were analyzed by molecular hybridization with complementary DNA (cDNA) synthesized from yeast poly(A)-containing mRNA with viral reverse transcriptase and ribosomal DNA labeled in vitro by nick translation with E. coli DNA polymerase I. RNA synthesized by polymerase I and II in the presence of Mn2+ contained sequences complementary to cDNA and rDNA at a frequency consistent with random transcription of the template. Similarly, E. coli RNA polymerase synthesized an apparently random transcript in the presence of either Mn2+ or Mg2+. In contrast to these results, RNA polymerase I but not polymerase II transcripts were markedly enriched in sequences complementary to rDNA when transcription was carried out in the presence of Mg2+. The observed enrichment was 15-30-fold higher than observed for polymerase II or E. coli polymerase transcripts and is consistent with the transcript being comprised of 6-10% ribosomal sequences. These data strongly suggest that RNA polymerase I plays a critical role in selective transcription of ribosomal cistrons.
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PMID:Transcription of yeast DNA by homologous RNA polymerases I and II: selective transcription of ribosomal genes by RNA polymerase I. 31 52

We found a type D retrovirus in a human lymphoblastoid cell line of B-cell lineage. Molecular cloning and nucleotide sequencing of the provirus genome revealed that this virus was closely related to squirrel monkey retrovirus (SMRV), and we designated this virus as SMRV-H. To investigate the relationship between these retroviruses, SMRV-H was purified from the virus-producing cells, and its biochemical properties were characterized. The cell-adhesive virus particles were successfully separated from the cell by a brief trypsin treatment and purified by velocity sedimentation. The purification of the virus was confirmed by electron microscopy. Major gag protein of the virus is phosphorylated, and has a molecular weight of 34 kDa. The virion-associated reverse transcriptase prefers Mg2+ to Mn2+. These properties of SMRV-H were almost the same as those of SMRV.
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PMID:Purification and biochemical characterization of squirrel monkey retrovirus-H produced in a human lymphoblastoid cell line. 128 48


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