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

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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)

The [2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]-3'- spiro-5"-(4"-amino-1",2"-oxathiole-2",2"-dioxide) (TSAO) derivatives of N1-methylhypoxanthine with linkage to the TSAO moiety through the N9 or N7 atom of the hypoxanthine ring (designated TSAO-m1Hx and 7-TSAO-m1Hx, respectively) are potent and selective inhibitors of human immunodeficiency virus type 1 (HIV-1) but not HIV-2 or simian immunodeficiency virus. Their selectivity indices (ratio of cytotoxic concentration to antivirally active concentration) are > 500. This is a > 15-fold increase in therapeutic index, compared with TSAO-adenine. A HIV-1(IIIB) variant selected for resistance to TSAO-m1Hx (designated HIV-1/TSAO-m1Hx) proved to be cross-resistant to the other TSAO-purine derivatives and to the TSAO-pyrimidine derivatives. However, HIV-1/TSAO-m1Hx was highly sensitive to the HIV-1-specific non-nucleoside tetrahydroimidazobenzodiazepinone, nevirapine, pyridinone L697,661, and several HEPT derivatives. The reverse transcriptase (RT) of HIV-1/TSAO-m1Hx shows a single amino acid change (138-Glu to Lys) that is identical to the amino acid change that has recently been observed in several HIV-1/TSAO-pyrimidine mutant strains. Our observations indicate that the TSAO-purines and TSAO-pyrimidines belong to one pharmacological class of HIV-1-specific RT inhibitors that are targeted at the same molecular site of the HIV-1 RT.
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PMID:Human immunodeficiency virus type 1-specific [2',5'-bis-O-(tert- butyldimethylsilyl)-beta-D-ribofuranosyl]-3'-spiro-5"-(4"-amino-1",2"- oxathiole-2",2"-dioxide)-purine analogues show a resistance spectrum that is different from that of the human immunodeficiency virus type 1-specific non-nucleoside analogues. 767 89

Site-directed mutagenesis has been used to assess the importance of lysine 263 in substrate binding of human immunodeficiency virus-1 (HIV-1) reverse transcriptase. Previous studies have indicated that lysine 263 functions in the binding of 2'-deoxynucleoside 5'-triphosphate (dNTP) substrates (Basu, A., Tirumalai, R. S., and Modak, M. J. (1989) J. Biol. Chem. 264, 8746-8752). We studied this interaction directly by using site-specific mutagenesis to change lysine 263 to a serine. Highly purified mutant enzyme K263S bound natural dNTP substrates and primed polynucleic acid substrates with equal affinity when compared to the wild type reverse transcriptase. No difference was observed in the binding of 3'-azido-2',3'-dideoxythymidine 5'-triphosphate to the mutant reverse transcriptase on the basis of Km and Ki determinations. The serine substitution had no effect on RNase H activity. These results indicate that lysine 263 is not essential in the binding of substrates to HIV-1 reverse transcriptase.
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PMID:Biochemical analysis of human immunodeficiency virus-1 reverse transcriptase containing a mutation at position lysine 263. 767 98

Six affinity reagents containing chemically reactive groups, either on the phosphate residue at the 5'-end or on the 5'- or 3'-end internucleoside phosphate linkages of the oligothymidylate primers, were used to covalently modify the human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT). After covalent binding of these modified primer analogs to the enzyme, the addition of [alpha-32P]dTTP, in the presence of a complementary template, led to elongation of the primer. This reaction was catalyzed by the active site of the enzyme carrying the covalently bound primer. The relative efficiency of labeling of the p66/p51 heterodimer compared to the p66/p66 and p51/p51 homodimers of HIV-1 RT was in agreement with the previously determined affinity of the various enzyme forms toward different primers. The analogues preferentially modified the p66 subunit of the HIV-1 RT heterodimer. The labeling of all RT forms by synthetic primer analogues showed significant and specific competition by the natural primer of HIV-1 RT, tRNA(Lys). In addition, the kinetics of inactivation of RT by primer analogues was studied. The affinity of the enzyme to those derivatives in the presence of poly(A) template was about 5-10 times higher than in the absence of template. Moreover, the maximal rates of HIV-1 RT inactivation by analogues in the absence of template were 3-4 times higher. Our results suggest that the mechanism of oligonucleotide primer binding to HIV-1 RT is different in the presence or absence of template.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Affinity labeling and functional analysis of the primer binding domain of HIV-1 reverse transcriptase. 768 10

Packaging of the genomic RNA dimer and replication primer tRNA(Lys,3) into HIV virions are required for the production of infectious virus. The initiation of reverse transcription necessitates the annealing of tRNA(Lys,3) to the primer binding site (PBS) of HIV RNA by nucleocapsid (NC) protein. In this report the interactions of replication primer tRNA(Lys,3) with various forms of reverse transcriptase (RT) and nucleocapsid protein have been analyzed by ultraviolet light (UV) cross-linking and gel retardation assays. We show that of the three forms of RT studied, p66/p51, p66 and p51, only the heterodimer p66/p51 can tightly and stably interact with tRNA(Lys,3). Tight interactions between tRNA(Lys,3) and nucleocapsid protein, either NCp15 or NCp7, were found to take place within the anticodon domain. Interestingly enough, primer tRNA(Lys,3) can interact with RTp66/p51 and NCp15 to form a high molecular weight complex in which RTp66/p51 appears to enhance the binding of NCp15 to tRNA(Lys,3). These findings favor the notion that the RT enzyme and NC protein co-operate to select and package primer tRNA.
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PMID:Analysis of the interactions of HIV1 replication primer tRNA(Lys,3) with nucleocapsid protein and reverse transcriptase. 768 91

Nuclease footprinting has been used to probe features of binary complexes of type 1 human immunodeficiency virus reverse transcriptase (HIV-1 RT) with both natural and synthetic preparations of its cognate replication primer, tRNA(Lys-3). In addition to heterodimeric RT (p66/p51), ribonucleoprotein complexes containing either the p66 or p51 subunit were analyzed. Footprinting experiments employed both structure- and sequence-specific nucleases. Our results indicate a similar mode of interaction for the three RT preparations tested, suggesting contact with each loop of the tRNA primer (D, anticodon, and T psi C), as well as minor perturbation of the anticodon stem. Although there is little evidence for extensive disruption of the 3'-acceptor stem. RNase A footprinting data with natural and synthetic tRNA suggests that potential base pairing between the T psi C and D loops is disrupted in the presence of RT.
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PMID:Nuclease footprinting of human immunodeficiency virus reverse transcriptase/tRNA(Lys-3) complexes. 768 66

Serial passage of HIV-1 in CEM or MT-4 cell cultures in the presence of different HIV-1-specific reverse transcriptase (RT) inhibitors yielded mutant viruses which were resistant (i.e., 200- to 1000-fold less sensitive) to the homologous compounds. The RT of these mutant HIV-1 strains showed different amino acid substitutions depending on the class of the HIV-1-specific RT inhibitors. The following amino acid substitutions were found: 138 Glu-->Lys (TSAO-T), 181 Tyr-->Cys (nevirapine), 181 Tyr-->Cys (pyridinone), and 100 Leu-->Ile (TIBO R82150). Four TIBO (R82913)-resistant HIV-1 strains contained different amino acid substitutions: 103 Lys-->Asn (strain 2), 100 Leu-->Ile and 138 Glu-->Lys (strain B02), 100 Leu-->Ile and 181 Tyr-->Cys (strain 1), 100 Leu-->Ile and 188 Tyr-->His (strain B22). The level of cross-resistance (or sensitivity) highly depends on the nature of the amino acid substitutions. As a rule, the TSAO-resistant HIV-1 strains (138 Glu-->Lys) and TIBO (R82150 or R82913)-resistant HIV-1 strains (Leu 100-->Ile or 103 Lys-->Asn) are sensitive to the other HIV-1-specific RT inhibitors, whereas the amino acid change 181 Tyr-->Cys results in a significant reduction of sensitivity to all classes of the HIV-1-specific RT inhibitors.
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PMID:HIV-1-specific reverse transcriptase inhibitors show differential activity against HIV-1 mutant strains containing different amino acid substitutions in the reverse transcriptase. 768 64

Bisheteroarylpiperazines are potent inhibitors of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT). We describe a novel bisheteroarylpiperazine, U-90152 [1-(5-methanesulfonamido-1H-indol-2-yl-carbonyl)-4-[3-(1-methyl eth yl-amino)pyridinyl]piperazine], which inhibited recombinant HIV-1 RT at a 50% inhibitory concentration (IC50) of 0.26 microM (compared with IC50s of > 440 microM for DNA polymerases alpha and delta). U-90152 blocked the replication in peripheral blood lymphocytes of 25 primary HIV-1 isolates, including variants that were highly resistant to 3'-azido-2',3'-dideoxythymidine (AZT) or 2',3'-dideoxyinosine, with a mean 50% effective dose of 0.066 +/- 0.137 microM. U-90152 had low cellular cytotoxicity, causing less than 8% reduction in peripheral blood lymphocyte viability at 100 microM. In experiments assessing inhibition of the spread of HIV-1IIIB in cell cultures, U-90152 was much more effective than AZT. When approximately 500 HIV-1IIIB-infected MT-4 cells were mixed 1:1,000 with uninfected cells, 3 microM AZT delayed the evidence of rapid viral growth for 7 days. In contrast, 3 microM U-90152 totally prevented the spread of HIV-1, and death and/or dilution of the original inoculum of infected cells prevented renewed viral growth after U-90152 was removed at day 24. The combination of U-90152 and AZT, each at 0.5 microM, also totally prevented viral spread. Finally, although the RT amino acid substitutions K103N (lysine 103 to asparagine) and Y181C (tyrosine 181 to cysteine), which confer cross-resistance to several nonnucleoside inhibitors, also decrease the potency of U-90152, this drug retains significant activity against these mutant RTs in vitro (IC50s, approximately 8 microgramM).
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PMID:U-90152, a potent inhibitor of human immunodeficiency virus type 1 replication. 768 95

Human immunodeficiency virus type-1 (HIV-1) reverse transcriptase (RT) and its domain fragments were used to map nucleic acid binding sites within the enzyme. Discrete domain fragments were produced after the digestion of three forms of RT (p66, p66/p51 heterodimer, and p51) with V8 protease or trypsin, and the primary structure of each domain fragment was mapped by both immunoblotting and N-terminal amino acid sequence analysis. These domain fragments represent N-terminal, middle, or C-terminal regions of RT. Using Northwestern or Southwestern blotting assays, the domain fragments were evaluated for nucleic acid binding. In this technique, RT proteins are electroblotted onto the membrane and renatured after SDS-PAGE; the proteins are then probed with the primer analogues 32P-labeled d(T)16 or 32P-labeled tRNA(Lys,3). A V8 protease domain fragment spanning residues 195 to approximately 300 (p12), which was found earlier to be UV cross-linked to the primer in intact RT [Sobol et al. (1991) Biochemistry 30, 10623-10631], showed binding to both nucleic acid probes. We first localized nucleic acid binding in p66 to an N-terminal domain fragment of residues 1 approximately equal to 300. By contrast, a C-terminal domain fragment termed p30(303 approximately equal to 560) did not show nucleic acid binding. To investigate the role of the region just N-terminal to residue 303, an expression vector named pRC-35 encoding residues 273-560 was constructed.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mapping of nucleic acid binding in proteolytic domains of HIV-1 reverse transcriptase. 768 75

We recently reported that a newly discovered class of nucleoside analogues--[2',5'-bis-O-(tert-butyldimethylsilyl)- 3'-spiro-5''-(4''-amino-1'',2''-oxathiole-2'',2''-dioxide)]-beta-D - pentofuranosyl derivatives of pyrimidines and purines (designated TSAO)--are highly specific inhibitors of human immunodeficiency virus type 1 (HIV-1) and targeted at the nonsubstrate binding site of HIV-1 reverse transcriptase (RT). We now find that HIV-1 strains selected for resistance against three different TSAO nucleoside derivatives retain sensitivity to the other HIV-1-specific nonnucleoside derivatives (tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-one and -thione (TIBO), 1-[(2-hydroxyethoxy)methyl]-6-phenylthiothymine, nevirapine, and pyridinone L697,661, as well as to the nucleoside analogues 3'-azido-3'-deoxythymidine, ddI, ddC, and 9-(2-phosphonylmethoxyethyl)adenine. Pol gene nucleotide sequence analysis of the TSAO-resistant and -sensitive HIV-1 strains revealed a single amino acid substitution at position 138 (Glu-->Lys) in the RT of all TSAO-resistant HIV-1 strains. HIV-1 RT in which the Glu-138-->Lys substitution was introduced by site-directed mutagenesis and expressed in Escherichia coli could not be purified because of rapid degradation. However, HIV-1 RT containing the Glu-138-->Arg substitution was stable. It lost its sensitivity to the TSAO nucleosides but not to the other HIV-1-specific RT inhibitors (i.e., TIBO and pyridinone). Our findings point to a specific interaction of the 4''-amino group on the 3'-spiro-substituted ribose moiety of the TSAO nucleosides with the carboxylic acid group of glutamic acid at position 138 of HIV-1 RT.
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PMID:Human immunodeficiency virus type 1 (HIV-1) strains selected for resistance against the HIV-1-specific [2',5'-bis-O-(tert-butyldimethylsilyl)-3'-spiro- 5''-(4''-amino-1'',2''-oxathiole-2'',2''-dioxide)]-beta-D-pentofurano syl (TSAO) nucleoside analogues retain sensitivity to HIV-1-specific nonnucleoside inhibitors. 768 67

We have utilized UV-induced cross-linking of [methyl-3H]dTTP to identify the nucleotide binding site on heterodimeric HIV-1 reverse transcriptase (RT). RT was derivatized by irradiating a solution containing [methyl-3H]dTTP and purified recombinant RT for 10 min. The UV-induced cross-linking reaction between dTTP and RT is linear with time of UV exposure up to 10 min, and it has been determined previously that dTTP cross-linking is half-maximal at 90 microM [Cheng, N., Painter, G. R., & Furmann, P.A. (1991) Biochem. Biophys. Res. Commun. 174, 785-789]. Under these reaction conditions, only the 66-kDa subunit of the 66-kDa/51-kDa RT heterodimer was labeled with dTTP. The [methyl-3H]dTTP-labeled RT was fragmented with trypsin and endoproteinase Asp-N, and peptides were purified on reversed phase HPLC. The peptide covalently linked to [methyl-3H]dTTP was subjected to amino acid sequence analysis. The sequencing data localized the nucleotide binding site of RT to Lys-73 in the vicinity of several mutation sites linked to antiviral drug resistance. Since most effective anti-AIDS compounds are inhibitors of RT, information about its dNTP binding site may make it possible to understand the basis for the antiviral activity of nucleoside analogs such as AZT, ddI, and ddC. This information may also be useful for a more rationally based design of anti-HIV agents.
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PMID:Identification of the nucleotide binding site of HIV-1 reverse transcriptase using dTTP as a photoaffinity label. 768 65


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