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

---

Query: EC:2.7.7.48 (transcriptase)
9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Reverse transcriptase from the simian immunodeficiency virus (SIV) was found to have kinetic behavior similar to that of enzyme from the human immunodeficiency virus (HIV). Michaelis constants for the substrates TTP and dGTP and inhibition constants for the inhibitors 3'-azido-3'-deoxythymidine 5'-triphosphate, 2',3'-dideoxythymidine 5'-triphosphate, and 2'-3'-dideoxyguanosine 5'-triphosphate were obtained for SIV reverse transcriptase and were found to be similar to the corresponding values for HIV reverse transcriptase. Thus, the interaction of SIV reverse transcriptase with nucleotide analogs appears to be indistinguishable from that of the HIV enzyme, suggesting that SIV/simian acquired immunodeficiency syndrome (SAIDS) is a potentially good model of AIDS.
...
PMID:Kinetics and inhibition of reverse transcriptase from human and simian immunodeficiency viruses. 246 88

Reverse transcriptase activity was tested in 65 patients with non-A,non-B hepatitis, with positive results in 2 acute sporadic cases with favorable outcome. Virus-like particles were observed in ultra-thin sections of successive serum samples from one of the reverse transcriptase activity-positive patients by electron microscopy. These results suggest that some non-A,non-B hepatitis types could be related to a virus-like agent associated with a reverse transcriptase activity.
...
PMID:Virus-like particles associated with reverse transcriptase activity in acute sporadic non-A,non-B hepatitis. 247 89

The kinetics of forming all possible single base substitution errors are measured for Drosophila melanogaster DNA polymerase alpha and avian myeloblastosis virus reverse transcriptase. Seventeen sites along bacteriophage M13 DNA are investigated so that effects of nearest neighbor base stacking on misinsertion kinetics can be evaluated. Polymerase alpha appears to be more error prone than reverse transcriptase. Polymerase alpha forms transversion mispairs at rates comparable to transition mispairs with two exceptions; A.A and C.C are formed with significantly higher and lower efficiencies, respectively. Reverse transcriptase forms transversions with lower efficiencies than transitions, especially low being A.G, G.G, and C.C. For both enzymes, misinsertion frequencies vary typically by 10-fold for the same mispair in different locations. Misinsertion frequency can be expressed as a product of two components, one based on Km and the other on Vmax. DNA polymerase alpha appears to use primarily Km discrimination (100-5000-fold) to achieve insertion fidelity while reverse transcriptase shows a greater balance between Km and Vmax discrimination. Nearest-neighbor base stacking interactions appear to have opposite effects on the two discrimination components. The 5'-nearest neighbor influence on Km is greater for correct insertions than for incorrect, while the influence on Vmax is greater for the incorrect base. Target sites that have pyrimidine as the 5'-nearest neighbor to incoming nucleotides show a higher than average misinsertion component based on Km, but a lower than average component based on Vmax. Conversely, target sites with nearest neighbor purines have a higher than average Vmax component. These results imply that nucleotide misinsertion "hot spots" will occur next to pyrimidines when Km discrimination is dominant and next to purines when Vmax discrimination is dominant. When Vmax and Km discrimination components have similar magnitudes, nearest neighbor effects tend to cancel thereby reducing the effects of base stacking on insertion error rates.
...
PMID:Nearest neighbor influences on DNA polymerase insertion fidelity. 247 45

Reverse transcriptase, discovered in 1970 in retroviruses, has until recently been found only in eukaryotic organisms. Recently it was shown to occur in two groups of bacteria: myxobacteria and Escherichia coli. The gene for reverse transcriptase is part of a chromosomal genetic element that codes for the production of a branched DNA-RNA compound. In this compound a single-stranded DNA is connected to RNA at a specific G residue by a 2'-5' phosphodiester linkage. The precursor for the DNA-RNA compound is a folded messenger RNA, in which the specific G residue is the initiation point for reverse transcription. In the final DNA-RNA compound, the portion of the RNA transcribed by reverse transcriptase is eliminated by RNase H. The DNA-RNA compound is present in several hundred copies per cell. Its biological function is unknown at present.
...
PMID:Reverse transcriptase in bacteria. 248

Antibodies raised against intercellular fluid antigens isolated from diseased tomato leaves have revealed that the fungal pathogen Fulvia fulva expresses genes for a fungal reverse transcriptase (RNA-dependent DNA polymerase). This enzyme is required for the replication of retroviruses and retroviral-like transposable elements and could provide a mechanism for increasing the mutation rate of fungal pathogens, perhaps explaining their ability to evolve new races rapidly. We report here the DNA sequence of a 225-bp clone from a lambda gt11 genomic library of F. fulva. This clone, designated P5, exhibits a high degree of sequence homology with the reverse transcriptase (pol) gene of the Drosophila melanogaster copia-like retrotransposon 17.6. Southern blot analysis of genomic DNA of F. fulva showed that P5-related sequences are moderately reiterated with 30-100 copies, some of which exhibit restriction fragment length polymorphism in different races of the pathogen. Western blot analysis of extracts from F. fulva with antibodies raised to purified reverse transcriptase (from human immunodeficiency virus-1) revealed immunoreactive proteins. Reverse transcriptase previously has been detected in a variety of organisms including yeast, insects, protozoa, and mammals, but to our knowledge, this is the first report of its occurrence in filamentous fungi.
...
PMID:Expression of reverse transcriptase genes in Fulvia fulva. 248 12

The retroviruses human T-cell lymphotrophic virus-I (HTLV-I) and HTLV-III/LAV (lymphadenopathy-associated virus) are clearly linked to human diseases. Patients with HTLV-I-positive neoplasms may respond transiently to traditional chemotherapy, but are not cured. For patients with acquired immune deficiency syndrome (AIDS) there is no curative therapy. In retroviruses of different species, viral propagation crucially depends on reverse transcriptase, an enzyme not present in normal mammalian cells and different from mammalian DNA polymerases, making it a target for specific inhibition. Reverse transcriptase has been well conserved through evolution: an LAV isolate contained a 250-amino-acid-long domain, presumably the reverse transcriptase core sequence, which has 21% homology to Moloney murine leukaemia virus (MoMLV). Because HTLV-III infects only humans and chimpanzees, we substituted murine retroviruses for in vivo evaluation of candidate anti-AIDS drugs after ascertaining similar inhibition in vitro of HTLV-III and MLVs, which were chosen for their short incubation time. The triphosphate of 3'-azido-3'-deoxythymidine (AZT) is incorporated into complementary DNA by retroviral reverse transcriptase, causing premature chain termination. Here we show that chronic AZT treatment of mice infected with Rauscher murine leukaemia virus complex (RLV) prevents infection of splenocytes and development of splenomegaly, and suppresses viraemia if started soon after inoculation. Starting AZT late in the course of disease still leads to significant prolongation of life; anaemia, however is a significant side-effect. By analogy, AZT may have a role in preventing retroviral disease in humans if started early after infection, and it may lead to significant survival gains even if started later in the course of disease.
...
PMID:Suppression of mouse viraemia and retroviral disease by 3'-azido-3'-deoxythymidine. 346 67

Pichinde virus, a member of the arenavirus group, was examined for polymerase activity. Purified virus was found to contain RNA-dependent RNA polymerase but not RNA-dependent DNA polymerase activity. Since RNase but neither DNase nor actinomycin D inhibited the endogenous polymerase reaction, RNA of the virus appeared to be used as the template. The divalent cations Mg(2+) and Mn(2+) were required for optimal reactivity. The RNA product was partially resistant to RNase and the resistant portion had a sedimentation coefficient of 22 to 26S in sucrose gradients.
...
PMID:Polymerase activity of Pichinde virus. 413 69

The availability of a purified RNA-instructed DNA polymerase (reverse transcriptase) from avain myeloblastosis virus provided the opportunity to explore whether this enzyme could be used as a general tool for synthesizing DNA complements of a wide variety of natural RNAs. The results described show that this potentially useful situation is in fact realized. The avian viral transcriptase can mediate the synthesis of DNA complementary to RNAs of such widely divergent origins as Qbeta bacteriophage and Moloney sarcoma virus. These findings open up novel pathways for the experimental resolution of several interesting problems. Thus, given a purified RNA message, one should be able to synthesize the corresponding DNA genetic material. If suitably labeled, the synthetic DNA has various obvious uses, including its use via molecular hybridization as an analytical probe for the corresponding gene on the chromosomes or for its message in a complex mixture of RNA molecules. Of immediate practical interest is the import of these findings for viral oncology. They imply that for many purposes we will not be compelled to isolate or use the "reverse transcriptase" from each oncogenic virus in order to synthesize its complementary DNA. The ability of one enzyme to accept a variety of oncogenic RNAs will obviate many of the logistical difficulties that arise, particularly in attempts to illuminate the etiology of human cancer.
...
PMID:Synthesis of DNA complements of natural RNAs: a general approach. 433 Sep 45

Assays are described that permit one to distinguish the reverse transcriptase of RNA tumor viruses from known normal cellular DNA-instructed DNA polymerases. Template responses of purified reverse transcriptase were compared with those of similar preparations of the DNA polymerase I of Escherichia coli and of calf-thymus polymerase. All three enzymes responded well to the synthetic duplexes poly(dT).poly(A), poly(U).poly(A), and poly(dT).poly(dA). Hence, these duplexes can detect, but cannot distinguish reverse, transcriptase from the known normal DNA polymerases. However, certain oligomer-homopolymer complexes serve as excellent distinguishing agents. The reverse transcriptase responds very well to (dT)(10).poly(A) and very poorly to (dT)(10).poly(dA), whereas both cellular DNA polymerases do not exhibit this behavior.Purified single-stranded RNA also serves as a diagnostic device, since only reverse transcriptase gives a detectable response. To be definitive, a positive response to RNA must be accompanied by a demonstration via molecular hybridization that the DNA product is complementary to the RNA and not to some minor DNA contaminant.
...
PMID:Distinguishing reverse transcriptase of an RNA tumor virus from other known DNA polymerases. 433 48

Influenza B/LEE/40, B/Rome/1/67, B/Hong Kong/8/73, and B/Victoria/98926/70 viruses have a similar polypeptide composition as analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. These viruses are composed of six or seven polypeptides, depending on whether one or two high-molecular-weight polypeptides are resolved, ranging in molecular weights from 27,000 to 90,400. Three of these polypeptides, namely the heavy and light hemagglutinin chains and the neuraminidase, have attached carbohydrate. Highly purified influenza B/LEE/40 and B/Rome/1/67 virus preparations have RNA-dependent RNA polymerase activity equivalent to the incorporation of 100 and 30 pmol, respectively, of (3)H-UMP per mg of virus protein per h at 37 C, which is demonstrated only in detergent-treated virus suspensions. However, no RNA-dependent DNA polymerase enzyme activity was detected in the two viruses although virus suspensions were "activated" by heat, alpha-chymotrypsin, and detergents. Other enzymatic activities were associated with purified preparations of influenza B virus and were attributed to minor contamination of virus with host cell enzymes. Thus, nucleoside and deoxynucleoside phosphohydrolase enzymes were active in the absence of detergents and catalyzed the release of 1,200 and 1,800 nmol of P(i) per mg of virus protein in 30 min at 37 C from ATP and dATP substrates. Thin-layer chromatography indicated that the products of the phosphohydrolase enzymes of influenza B/LEE/40 were mainly nucleoside diphosphate and monophosphate. The latter enzymes were tightly bound to influenza B/LEE/40 virus and could not be removed completely by repeated centrifugation, including centrifugation of the virus to equilibrium in density gradients of 25 to 40% (wt/vol) cesium chloride. A low degree of RNase (approximately 0.01 mug% contamination) and phosphatase (10-30 nmol of P(i) released per mg of virus protein per 30 min) activity was detected in some, but not all, influenza B/LEE/40 virus preparations.
...
PMID:Polypeptide composition of Influenza B viruses and enzymes associated with the purified virus particles. 435 55


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---