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:3.1.26.4 (RNase H)
2,751 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied the effect of the natural marine substance illimaquinone on the catalytic activities of reverse transcriptase from human immunodeficiency virus type 1. Illimaquinone inhibited the RNase H activity of the enzyme at concentrations of 5 to 10 microgram/ml, whereas RNA-dependent DNA polymerase and DNA-dependent DNA polymerase activities were considerably less susceptible to this inhibition. Two synthetic derivatives of illimaquinone, in which the 6'-hydroxyl group at the ortho position to one of carbonyl groups of the quinone ring was modified, proved ineffective in inhibiting the human immunodeficiency virus type 1 reverse transcriptase RNase H function, suggesting involvement of the 6'-hydroxyl group in blocking the enzymatic activity.
...
PMID:Illimaquinone, a selective inhibitor of the RNase H activity of human immunodeficiency virus type 1 reverse transcriptase. 170 12

The RNA- and DNA-dependent DNA polymerase activities of two point mutants of HIV-1 reverse transcriptase lacking ribonuclease H activity have been compared to the wild-type enzyme activities using substrates consisting of an oligodeoxynucleotide primer hybridized to either a RNA or a DNA template. The RNase H phenotype had a negligible effect on the steady-state kinetics and processivity of reverse transcription of a homopolymer template-primer [poly(A).oligo(dT)]. However, analysis of the distribution of DNA products indicated that the ability of the mutants to reverse-transcribe a specifically primed 345-nucleotide heteropolymeric RNA template derived from the gag region of HIV-1 was impaired relative to the wild-type enzyme. Although the wild-type and mutant enzymes shared the same pause sites of synthesis along the RNA template, certain prematurely terminated nascent primer chains were poorly extended by the mutant enzymes and hence accumulated, suggesting that a catalytically functional RNase domain facilitated reinitiation of DNA synthesis at specific pause sites along a heteropolymer template. In contrast, the processivity and product distribution of DNA synthesis directed by a heteropolymer gag DNA template of the same nucleotide sequence were not significantly influenced by the RNase H phenotype of the mutants.
...
PMID:Analysis of the RNA- and DNA-dependent DNA polymerase activities of point mutants of HIV-1 reverse transcriptase lacking ribonuclease H activity. 171 22

We have constructed a series of plasmids which, when introduced into Escherichia coli, induce the overexpression of soluble wild-type and mutated forms of the reverse transcriptases (RTs) from human immunodeficiency viruses types 1 and 2 (HIV-1 and HIV-2, respectively). These proteins were analyzed previously for their RNA-dependent DNA polymerase (RDDP) and ribonuclease H (RNase H) activities. In the present study we assayed the different mutant RTs for their DNA-dependent DNA polymerase (DDDP) activity, employing an in situ polyacrylamide gel activity assay. The results indicate that both the RDDP and DDDP catalytic functions of HIV-1 RT mutants are affected similarly by mutations suggesting a high degree of overlap between the catalytic domains involved in both activities. Contrariwise, many of the HIV-2 RT mutants display no correlation between these two DNA polymerase activities, that is, the DDDP activity was not affected by the mutations introduced in the native enzyme in contrast to the RDDP activity. We were thus able to generate mutants of HIV-2 RT that unlike the wild-type RT, are capable of transcribing only DNA and not RNA. The disparity in mutational-catalytic relations between the two HIV-related RTs may reflect a possible difference in the structure and folding properties of the two proteins.
...
PMID:The DNA-dependent and RNA-dependent DNA polymerase activities of the reverse transcriptases of human immunodeficiency viruses types 1 and 2. 172 5

An RNA-dependent DNA polymerase was isolated from purified virions of endogenous oncornaviruses released by the MOPC-315 murine myeloma cell line. Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the purified enzyme was found to consist of two major polypeptides with molecular weights of about 28,000 and 26,500. The active enzyme had a molecular weight of approximately 56,000, as calculated from its sedimentation on glycerol density gradients, indicating that it is probably a dimer of the two subunit polypeptides. The isolated MOPC-315 virus polymerase exhibited all three activities known to be found in the DNA polymerase from oncornaviruses, namely, an RNA-dependent DNA polymerase, a DNA-dependent DNA polymerase, and an RNase H. The RNA-dependent polymerase activity showed a prounced preference for Mn2+ over Mg2+, whereas the DNA-dependent and RNase H reactions were catalyzed by these two cations to an almost equal extent. The purified polymerase was found to be immunologically related to the polymerase of Rauscher murine leukemia virus.
...
PMID:RNA-dependent DNA polymerase of an endogenous type C virus of mice: purification and partial characterization. 615 78

A comparative study of recombinant 51- and 66-kDa subunits comprising equine infectious anemia virus reverse transcriptase (EIAV RT) is reported. Both polypeptides sedimented as stable homodimers (molecular mass, 102 and 132 kDa, respectively) when analyzed by rate sedimentation through glycerol gradients. Consistent with their dimer composition, each preparation displayed considerable levels of both RNA- and DNA-dependent DNA polymerase activity on different homopolymeric template/primer combinations. However, a detailed analysis of the polymerization products indicated qualitative differences. Whereas p66 EIAV RT proceeded essentially unimpaired along both RNA and DNA templates, p51-catalyzed DNA synthesis was interrupted close to or in the immediate vicinity of the primer. A series of "programmed" 2-step polymerization reactions suggests that p51 EIAV RT enters an abortive mode of polymerization. Duplication of this observation with p51 human immunodeficiency virus-1 RT, together with recent observations from murine RT, suggests that lack of a ribonuclease H domain and loss of contact with the nascent product from the polymerase active center have profound consequences on the mode of polymerization.
...
PMID:Alternative modes of polymerization distinguish the subunits of equine infectious anemia virus reverse transcriptase. 751 Jun 90

Activity against human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) in the organic extract of the Red Sea sponge Toxiclona toxius was traced by us to five novel natural compounds, namely toxiusol [1], shaagrockol B [3], shaagrockol C [4], toxicol A [6], all of which are sulfated hexaprenoid hydroquinones, and toxicol B [7], the p-hydroquinone derivative of compound 6. The hydrolysis of the two sulfated compounds 1 and 4 yielded the corresponding hydroquinones designated as compounds 2 and 5, and further oxidation of compound 7 afforded the corresponding p-quinone derivative, compound 8. All compounds exhibited inhibitory activity of both DNA polymerizing functions of HIV-1 RT but failed to inhibit the RT-associated ribonuclease H activity. Toxiusol [1] was found to be the most potent inhibitor of the RNA-dependent DNA polymerase function (with 50% inhibition obtained at 1.5 microM and 95% inhibition at 4.6 microM), whereas the DNA-dependent DNA polymerase was significantly less sensitive to the inhibitor (with 50% inhibition achieved at 6.6 microM and 95% inhibition only at 41.6 microM). The fact that compound 1 discriminates between the two DNA polymerase activities of the RT offers new prospects for developing potent and highly specific anti-RT compounds, since the RNA-dependent DNA polymerase activity of RT is the only unique function that is not expressed at significant levels in uninfected mammalian cells.
...
PMID:Hexaprenoid hydroquinones, novel inhibitors of the reverse transcriptase of human immunodeficiency virus type 1. 751 Jul 86

The natural product of the Red Sea sponge Verongia sp., identified as 3,5,8-trihydroxy-4-quinolone, was found to be a potent inhibitor of the RNA-directed DNA synthesis of the reverse transcriptases (RTs) of human immunodeficiency viruses type 1 and type 2 (HIV-1 and HIV-2, respectively). This inhibition was unaffected by the nature of the primer template used for DNA synthesis. The DNA-dependent DNA polymerase activity was inhibited to a lesser extent, whereas the ribonuclease H (RNase H) function associated with both HIV RTs was only slightly inhibited. The inhibition by the trihydroxyquinolone is reversible and noncompetitive with respect to both substrates--dTTP and the template primer poly(rA)n.oligo(dT)12-18. The inhibitor binds HIV-1 RT with a high affinity (Ki = 0.46 microM). This compound was shown also to inhibit the catalytic activities of the RT of murine leukemia virus, establishing the general inhibitory effect on retroviral RTs. Introductions of acetyl or methoxy moieties at positions with potential activity have generated three synthetic analogs of the natural compound. Only one analog, 5,8-dimethoxy-4-quinolone, exhibited an inhibition potency similar to that of the unmodified compound. Analysis of the three analogs has led us to the conclusion that the hydroxyl group at the ortho position to the carbonyl group in the pyridinone ring is a key structural element for the inhibitory activity. Thus, it could well be that the inhibitor interacts with the enzyme through a hydrogen bond of this hydroxyl group. We hope that the identification of the inhibitory site of the compound might be an important step toward the rational design of new potent anti-HIV RT drugs.
...
PMID:3,5,8-Trihydroxy-4-quinolone, a novel natural inhibitor of the reverse transcriptases of human immunodeficiency viruses type 1 and type 2. 751 Sep 44

Over 25 selected naphthalenesulfonic acid derivatives were evaluated for their inhibitory effect on two different functional domains of the HIV-1 reverse transcriptase (RT), namely the ribonuclease H and DNA polymerase activities. Most of the analogues were found to be either specific toward the DNA polymerase activity or showed nonselective inhibition of both catalytic functions. The most active compounds are either symmetrical derivatives or nonsymmetrical derivatives containing a lipophilic appendage consisting of a palmitoyl or cholesteryl moiety. The six most active compounds in the preliminary screen, derivatives 6, 16, 17, 23, 26, and 27, were subjected to experiments to determine their 50% inhibitory concentration (IC50) values in the assays that measure RNA-dependent DNA polymerase (RDDP), DNA-dependent DNA polymerase (DDDP), and ribonuclease H (RNase H) functions of HIV-1 RT. The most potent derivative was a nonsymmetric cholesterol-linked 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid analogue, compound 23, which demonstrated an IC50 value of 0.06 microM for inhibiting RDDP activity. Inhibition of DDDP and RNase H activity for this compound was demonstrated at concentrations that were over 100-fold of that for inhibiting RDDP activity. However, the potency of this active compound does not correlate in the whole virus assay, probably due to a lack of cellular entry. The cholesterol derivative, 23, also possesses HIV-1 protease inhibitory activity and belongs to a unique class of multifunctional HIV-1 inhibitors.
...
PMID:Synthesis of naphthalenesulfonic acid small molecules as selective inhibitors of the DNA polymerase and ribonuclease H activities of HIV-1 reverse transcriptase. 752 80

We have analyzed the human immunodeficiency virus type-1 reverse transcriptase (HIV-1 RT) polymerase domain between amino acids 91 and 157 by site-directed mutagenesis. We have constructed a series of amino acid substitutions using BspMI cassettes, and have assayed the RNA-dependent DNA polymerase, DNA-dependent DNA polymerase, and RNase H activities of the mutant HIV-1 RTs. The regions of HIV-1 RT between amino acids 91 and 119 and between amino acids 151 and 157 lie within the palm subdomain and include part of the polymerase active site. A number of amino acids within these regions have been identified as being directly or indirectly involved with polymerization, since amino acid substitutions at these residues decrease the polymerase activity without affecting RNase H activity. The region of HIV-1 RT between amino acids 120 and 150 lies within the fingers subdomain of the HIV-1 polymerase. We believe that the fingers subdomain plays a role in positioning the template. Many amino acid substitutions in this region decrease or abolish both the polymerase and the RNase H functions.
...
PMID:Mutational analysis of the fingers and palm subdomains of human immunodeficiency virus type-1 (HIV-1) reverse transcriptase. 752 67

Two new sesquiterpene hydroquinones, peyssonol A and peyssonol B, of the Red Sea algae Peyssonelia sp., have been shown to be potent inhibitors of the RNA-directed DNA synthesis of the reverse transcriptases (RTs) of human immunodeficiency virus (HIV)-1 and HIV-2. The DNA-dependent DNA polymerase activity is inhibited to a lesser extent, whereas the RNase H activity is unaffected. The inhibition of the DNA polymerase activities is independent of the nature of the template primers used. Peyssonol A probably binds the RT at a site distinct from those occupied by the substrates of the RNA-directed DNA synthesis, since the mode of inhibition is noncompetitive with respect to both dNTP's and template primer. This is partially true for peyssonol B, which is noncompetitive with respect to only dNTP, but is competitive with respect to the template primer. We have speculated that, since peyssonol B and the template primer bear no apparent structural resemblance, the competitive pattern of inhibition can be explained by an indirect steric hindrance or by the overlap of the inhibitor and the substrate distinct binding sites of the enzyme. Alternatively, the binding of the inhibitor to a distinct site induces conformational changes that distort the binding of the template primer. Furthermore, we have shown that both peyssonol A and peyssonol B interfere with the direct binding of the RT to the template primer, offering an explanation for the mechanism of the enzyme inhibition. The insensitivity of DNA polymerase beta and the poor response of DNA polymerase alpha to peyssonol A make this inhibitor more attractive for the future development of a potent anti-HIV RT drug.
...
PMID:Peyssonols A and B, two novel inhibitors of the reverse transcriptases of human immunodeficiency virus types 1 and 2. 753 86


<< Previous 1 2 3 4 5 Next >>

---