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)

Thiobenzimidazolone (TIBO) derivatives are known inhibitors of the DNA polymerase activity of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT). The effect of a TIBO derivative ((+)-S-4,5,6,7-tetrahydro-9-chloro-5- methyl-6-(3-methyl-2-butenyl)-imidazol[4,5,1-jk]1,4-benzodiazapine -2-thione ) on the DNA strand transfer reaction catalyzed by HIV-1 RT (which is a function of both the DNA polymerase and RNase H activities) was investigated by delineating the effect of the drug on the constitutive DNA polymerase and RNase H activities) was investigated by delineating the effect of the drug on the constitutive DNA polymerase and RNase H activities. Single nucleotide incorporation on template-primer 1 was used to study the DNA polymerase activity of HIV-1 RT while template-primer 2 was used to study the effect of TIBO on the RNase H activity (polymerase independent). The drug was found to decrease the amplitude of the presteady-state burst when preequilibrated with the enzyme-substrate complex besides decreasing the steady-state rate of single nucleotide incorporations. In the absence of preincubation, TIBO did not affect the burst amplitude but decreased the steady-state rate after the pre-transient phase. This suggested that binding of TIBO to RT was affected by the presence of template-primer and required dissociation of the enzyme from the template-primer for effective binding. The polymerase-independent RNase H activity was activated in the presence of TIBO. The effect of TIBO on the overall process of DNA strand transfer is a balance between its inhibition of the polymerase activity and its activation of the RNase H activity.
...
PMID:Effect of a thiobenzimidazolone derivative on DNA strand transfer catalyzed by HIV-1 reverse transcriptase. 750 39

In the presence of Mn2+, reverse transcriptase of both human immunodeficiency virus and murine leukemia virus hydrolyzes duplex RNA. However, designating this novel activity RNase D conflicts with Escherichia coli RNase D, which participates in tRNA processing. On the basis of its location in the RNase H domain, we propose that this novel retroviral activity be redesignated RNase H*.
...
PMID:Redesignation of the RNase D activity associated with retroviral reverse transcriptase as RNase H. 750 4

The reverse transcriptase (RT) of equine infectious anemia virus (EIAV) shares sequence similarity with the RTs of other lentiviruses, particularly with the RTs of human immunodeficiency viruses types 1 and 2 (HIV-1 and HIV-2, respectively), the causative agents of acquired immunodeficiency syndrome (AIDS). There is a 41-42% sequence identity between EIAV RT and both HIV RTs (which have 61% sequence identity to each other). We have compared the enzymic properties of EIAV RT with those of HIV-1 RT. Several aspects of the activities of EIAV RT differ from the corresponding activities of HIV-1 RT. There are significant differences in the inhibition of the DNA polymerase activities by the deoxynucleoside triphosphate analogs, 3'-azido-2,3'-dideoxythymidine triphosphate, dideoxyTTP and dideoxyGTP and by the nonnucleoside inhibitor, tetrahydroimidazo[4,5,1-jk-1,4]benzodiazepin-2-(1H)-one and thione; in the dependence of DNA polymerase and RNase H activities on pH; in the inhibition of the DNA polymerase activities by the thiol-specific reagent N-ethylmaleimide; in the specific DNA polymerase activity; in the inhibition of the ribonuclease H activity by the zinc chelator orthophenanthroline. However, there are several cases in which EIAV RT and HIV-1 RT are more similar than was previously found for HIV-1 RT and HIV-2 RT. These include the Km values for the DNA polymerase activities, the heat stability of the DNA polymerase functions and the specific activity of the RNase H function.
...
PMID:The catalytic properties of the reverse transcriptase of the lentivirus equine infectious anemia virus. 750 81

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

A recombinant p66 form of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) can be obtained [(1991) Biotechnol. Appl. Biochem. 14, 69-81] from crude Escherichia coli extracts by immobilized metal affinity chromatography (IMAC). We have analyzed the p66 HIV-1 RT, isolated in the presence of 0.3 M imidazole, by gel permeation HPLC on Superose 12. The results show that it contains two major distinct p66 forms (24.1 min and 28.3 min peaks) which are distinguishable from the purified homodimeric (p66/p66) HIV-1 RT (22.2 min peak). Protein peak 1 (24.1 min) is converted to a 22.3 min peak upon storage for 20 h at 4 degrees C. Under identical conditions, the isolated peak 2 (28.3 min) appeared as a conformationally heterogeneous mixture elaborated by peaks at 22.3 min and 25.9 min. The protein species thus obtained were active in the RNA-dependent DNA polymerase and RNase H activity assays and produced heterodimeric HIV-1 RT upon incubation with the HIV-1 protease. When the IMAC-purified, imidazole-free homodimeric (p66/p66) form of the enzyme was incubated with 0.3 M imidazole for 16 h at 4 degrees C, protein peaks at 28.3 min (peak A) and 30.5 min (peak B) were isolated by gel permeation HPLC. While both of these p66-containing species were stable and displayed identical RNA-dependent DNA polymerase activities, the protein in peak B was only 50% active in RNase H function compared with the protein from peak A. These imidazole-mediated dissociation studies support the hypothesis of partial unfolding of one of the RNase H domains of the p66/p66 homodimer, suggesting that the p66 subunits are asymmetric in the native enzyme.
...
PMID:Human immunodeficiency virus type 1 (HIV-1) recombinant reverse transcriptase. Asymmetry in p66 subunits of the p66/p66 homodimer. 751 87

The human immunodeficiency virus type 1 (HIV-1) is the etiologic agent of AIDS. Replication of this virus requires the activity of a retrovirus encoded RNA-dependent DNA polymerase, or reverse transcriptase (RT). HIV-1 RT is required for the synthesis of the double-stranded proviral DNA from the single-stranded retroviral RNA genome. HIV-1 RT has two subunits of 66 kDa and 51 kDa. The 66-kDa subunit contains the DNA polymerase and RNase H domains whereas the 51-kDa subunit, obtained by proteolytic maturation of the former subunit, has only the DNA synthetic activity. Two recently reported crystal structures of HIV-1 RT have revealed the very asymmetric structure of this molecule. In addition to providing information concerning the mechanism of nucleic acid polymerization, biochemical and biophysical studies of this enzyme are providing key insights for the design of selective antiviral agents. The multiple activities displayed by reverse transcriptase in the replication of the retroviral genome ensure that this enzyme will remain at the forefront of antiviral strategies in the fight against AIDS and other retrovirus-related pathologies.
...
PMID:The reverse transcriptase of HIV-1: from enzymology to therapeutic intervention. 751 43

The effects of point mutations of the conserved Asp443, Glu478, Asn494, and Asp498 residues in the RNase H domain of human immunodeficiency virus type I (HIV-1) reverse transcriptase (RT) have been analyzed. The mutants fell into two classes: (i) functional RT, but not detectable ribonuclease H activity, and (ii) uncharacterizable phenotype due to protein instability in the context of the RT/protease Escherichia coli co-expression system (Mizrahi, V., Lazarus, G. M., Miles, L. M., Meyers, C. A., and Debouck, C. (1989) Arch. Biochem. Biophys. 273, 347-358). The only mutation in the former class was D443A, whereas those in the latter included D443E, E478D, E478Q, D498E, D443A/D498N, D443E/D498N, D443Q/D498N, N494A, N494D, and N494Q. The results were interpreted in terms of the x-ray crystal structure of the HIV-1 RNase H domain (Davies, J. F., II, Hostomaska, Z., Hostomsky, Z., Jordan, S. R., and Matthews, D. A. (1991) Science 252, 88-95) and a general acid-general base hydrolysis mechanism (Katayanagi, K., Okumura, M., and Morikawa, K. (1993) Proteins Struct. Funct. Genet. 17, 337-346). The data suggested that structural perturbations within the RNase H domain interfered with maturation of the pol precursor by HIV-1 protease. Analysis of selected D443/D498 double mutants suggested that the destabilization caused by the D498N mutation could be suppressed by the formation of a new hydrogen bond between Asn498 and Asn443.
...
PMID:Mutagenesis of the conserved aspartic acid 443, glutamic acid 478, asparagine 494, and aspartic acid 498 residues in the ribonuclease H domain of p66/p51 human immunodeficiency virus type I reverse transcriptase. Expression and biochemical analysis. 751 54

The reverse transcriptase from human immunodeficiency virus type 1 is a heterodimer consisting of one 66-kDa and one 51-kDa subunit. The p66 subunit contains both a polymerase and an RNase H domain; proteolytic cleavage of p66 removes the RNase H domain to yield the p51 subunit. Although the polymerase domain of p66 folds into an open, extended structure containing a large active-site cleft, that of p51 is closed and compact. The connection subdomain, which lies between the polymerase and RNase H active sites in p66, plays a central role in the formation of the reverse transcriptase heterodimer. Extensive and very different intra- and intersubunit contacts are made by the connection subdomains of each of the subunits. Together, contacts between the two connection domains constitute approximately one-third of the total contacts between subunits of the heterodimer. Conversion of an open p66 polymerase domain structure to a closed p51-like structure results in a reduction in solvent-accessible surface area by 1600 A2 and the burying of an extensive hydrophobic surface. Thus, the monomeric forms of both p66 and p51 are proposed to have the same closed structure as seen in the p51 subunit of the heterodimer. The free energy required to convert p66 from a closed p51-like structure to the observed open p66 polymerase domain structure is generated by the burying of a large, predominantly hydrophobic surface area upon formation of the heterodimer. It is likely that the only kind of dimer that can form is an asymmetric one like that seen in the heterodimer structure, since one dimer interaction surface exists only in p51 and the other only in p66. We suggest that both p51 and p66 form asymmetric homodimers that are assembled from one subunit that has assumed the open conformation and one that has the closed structure.
...
PMID:Structural basis of asymmetry in the human immunodeficiency virus type 1 reverse transcriptase heterodimer. 751 28


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

---