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:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The reverse transcriptase (RNA-dependent DNA nucleotidyltransferase) of the type C RNA virus produced by the human lymphoma cell line SU-DHL-1 was purified by ion-exchange chromatography of SU-DHL-1 culture fluids and repetitive affinity chromatography on poly(rC).agarose, as were the polymerases of several other type C viruses. The DHL-1 enzyme used template-primers at levels expected of a viral reverse transcriptase, and sodium dodecyl sulfate gel electrophoretic analysis of radioiodinated DHL-1 enzyme revealed a peak at a position corresponding to those of several other type C viral reverse transcriptases (namely, at 72,000-78,000 daltons). The purified enzyme was partially neutralized by antibodies specific for the reverse transcriptase of simian sarcoma virus. Two-dimensional analysis on thin-layer cellulose plates of tryptic hydrolysates of the radioiodinated enzymes of several viruses revealed that six peptides are common to the polymerases of simian sarcoma virus, gibbon ape leukemia virus, baboon endogenous virus, and the DHL-1 virus, and that two to four peptides are unique to each of these enzymes. The DHL-1 viral reverse transcriptase appears to be most closely related structurally to the enzymes of simian sarcoma virus, gibbon ape leukemia virus, and baboon endogenous virus. However, the DHL-1 viral enzyme differed from any one or combination of the other subhuman primate viral enzymes by virtue of its unique peptides. The implications of these findings with respect to the probable origin of the DHL-1 virus are discussed.
...
PMID:Characterization of the reverse transcriptase of a type C RNA virus produced by a human lymphoma cell line. 9 23

[3H]Uridine-labeled Rauscher leukemia virus was used to infect mouse embryo fibroblasts. After the infected cells were separated into nuclear and cytoplasmic fractions nucleic acid was extracted by sodium dodecyl sulfate-phenol-chloroform treatment and analyzed by Cs2SO4 and sucrose density gradient centrifugation. Between 45 and 70 min after infection a transient and synchronized shift of the acid-insoluble radioactive peak toward the RNA-DNA hybrid region occurred in both the nuclear and cytoplasmic fractions. The density of the cytoplasmic hybrid shifted to 1.56 g/ml (RNA equals about 50%), while the sedimentation rate decreased from 36 S to 14 S; however, the density of the nuclear hybrid shifted to 1.58-1.48 g/ml (RNA equals 57-17%, respectively), while its sedimentation rate remained about 65 S. The hybrids in both the nuclear and the cytoplasmic fractions still showed hybrid density after heat denaturation. The processes of the early stages of RNA tumor virus infection are discussed with regard to the functions of viral RNA-dependent DNA polymerase (reverse transcriptase) and a possible integration of viral genetic information into the host chromosome.
...
PMID:Fate of viral RNA of murine leukemia virus after infection. 16 22

Maleylated-human serum albumin (Mal-HSA) inhibited human immunodeficiency virus type-1 (HIV-1) infection of MT-4 cells in vitro. It was also found to inhibit the fusion between uninfected CD4+ cells (Molt-4 clone 8 cells) and HIV-1 infected cells (Molt-4/HIV-1) to form syncytia. To investigate the mechanism of the inhibition, a study was designed to determine whether Mal-HSA could bind to CD4+ cells. Mal-HSA could bind to both MT-4 cells and Molt-4 clone 8 cells with high affinity, Kd = 2.0 nM and Kd = 5.8 nM, respectively. However, Mal-HSA could neither inhibit anti CD4 antibody Leu 3a binding to Molt-4 clone 8 cells nor modulate the expression of CD4 molecules on the surface of the cells. Mal-HSA binding to Molt-4 clone 8 cells was completely inhibited by sulfated polysaccharides bearing anti-HIV activity, such as dextran sulfate, fucoidan and carrageenan. Other HIV-1 susceptible human T-cell lines, such as Molt-4, CEM-5, H-9 and HuT-78 cells, also have Mal-HSA binding sites showing a high affinity, Kd = 0.9 +/- 0.4 nM. Mal-HSA binding proteins of Molt-4 clone 8 cells were identified by ligand blotting as 155 and 220 kDa proteins. Unlike dextran sulfate, Mal-HSA could not inhibit reverse transcriptase activity of HIV-1. These results indicate that Mal-HSA inhibits HIV-1 infection and syncytia formation, and suggest that 155 and/or 220 kDa proteins of target cells are involved in HIV-1 adsorption and/or the membrane fusion between HIV-1 and target cells.
...
PMID:Maleylated human serum albumin inhibits HIV-1 infection in vitro. 128 31

Based upon our previous report indicating the presence of retrovirus-like particles in human gastric cancer cells, we analyzed the putative endogenous reverse transcriptase activity these particles should have. To evaluate the specificity of reverse transcription over that displayed by normal cellular DNA polymerases, the following discriminatory criteria were used: 1) resistance to high concentrations of Actinomycin D; 2) sensitivity to preincubation with ribonuclease A; 3) behavior in cesium sulfate isopycnic gradients and 4) size-shifting of putative template-product complexes after RNase exposure in agarose gel electrophoresis. We report a significant endogenous reverse transcriptase activity associated with membrane-encapsidated particles from terminally-illed patients but not in normal counterparts. Although these structures closely resemble retro viruses, a new model is proposed to explain our findings.
...
PMID:Further characterization of RNA-dependent-DNA polymerase activity in human gastric cancer. 128 60

L-696,229 is a potent and specific inhibitor of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase and is currently undergoing clinical evaluation. In vivo metabolism in rats was investigated using an intravenous bolus dose of 5 mg/kg [3H]L-696,229. The amount of radioactivity eliminated in bile and urine over a period of 6 hr was 60 and 22%, respectively. Radiochromatographic analysis of the bile and urine showed that L-696,229 was metabolized rapidly and completely to several common metabolites. Sequential oxidation at the alpha-position of the 5-ethyl group to an acetyl moiety, aromatic hydroxylation of the benzoxazole group (position C4', C6', or C7'), and subsequent sulfate conjugation were the major metabolic pathways as determined by the application of enzymatic hydrolysis, FAB-MS, and 1H- and 13C-NMR spectroscopies. The in vitro metabolism of this 2-pyridinone derivative with rat liver slices resulted primarily in hydroxylation at the 6-methyl and 5-ethyl groups. The 6-hydroxymethyl- and 5-alpha-hydroxyethyl analogs were also inhibitors of HIV-1 reverse transcriptase.
...
PMID:Metabolism of a new HIV-1 reverse transcriptase inhibitor, 3-[2-(benzoxazol-2-yl)ethyl]-5-ethyl-6-methylpyridin-2(1H)-one (L-696,229), in rat and liver slices. 128 69

Reverse transcription of retroviral genomes requires the action of an RNase H for template switching and primer generation. In this report, we compare enzymatic properties of the RNase H associated with the reverse transcriptase (RT) from feline immunodeficiency virus (FIV) and that from human immunodeficiency virus (HIV). Both enzymes displayed substrate preference for poly[3H](rG) . poly(dC) hybird over poly[3H](rA) . poly(dT) and cation preference for Mg2+ over Mn2+. Activity of the FIV RNase H upon poly(rG) . poly(dC) produced hydrolysis products from 1 to 6 nucleotides in length, similar to that reported for HIV. Dextran sulfates were effective inhibitors of both the FIV and HIV RNase H and RT activities. Nearly identical inhibition constants (0.12 nM) were obtained for all enzyme activities with dextran sulfate 500,000, while different inhibition constants were observed with dextran sulfate 8,000. Our results suggest that FIV and HIV RTs contain a conserved region that is sensitive to the larger dextran sulfate and that dextran sulfate 8,000 may interact at a different site or by a different mechanism.
...
PMID:RNase H activity associated with reverse transcriptase from feline immunodeficiency virus. 137 May 49

One hundred and fifty six pure natural products, which had previously been tested against HIV-1 reverse transcriptase, were evaluated for HIV-2 reverse transcriptase inhibitory activity. Compounds that lacked effect in the HIV-1 reverse transcriptase system were found also to be inactive against HIV-2 reverse transcriptase. However, compounds belonging to the benzophenanthridine and protoberberine classes of alkaloids, certain flavonoids, the iridoid, fulvoplumierin, and the ansamycin antibiotic, daunomycin, exhibited similar potencies in both enzyme systems. In contrast, HIV-2 reverse transcriptase was observed to be four-fold more sensitive toward the inhibitory effects of the ipecac alkaloids, O-methylpsychotrine sulfate heptahydrate and psychotrine dihydrogen oxalate. Such differences in susceptibilities to inhibitors may indicate subtle dissimilarities in enzyme structure and function.
...
PMID:HIV-1 and HIV-2 reverse transcriptases: a comparative study of sensitivity to inhibition by selected natural products. 137 18

Active recombinant reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) with an amino-terminal extension containing a hexa-histidine sequence has been prepared in milligram quantities in a pure heterodimeric (p66/p51) form by coordinated applications of immobilized metal affinity chromatography (IMAC) and HIV-1 protease treatment. The precursor protein, isolated from extracts of recombinant Escherichia coli by IMAC in a predominantly unprocessed form (p66), migrated on sodium dodecyl sulfate-polyacrylamide gels as a 66-kDa band with minor heterogeneity at lower relative molecular mass. Incubation of this protein with recombinant HIV-1 protease produced a stable heterodimeric RT that was purified in a single step by IMAC. The purified protein retained both RT and RNase H activity, and kinetic parameters (Km and Vmax) were measured with both RNA-dependent DNA polymerization and RNase H activity assays. Carboxyl-terminal sequencing of purified heterodimeric RT indicated that one subunit is intact p66, whereas the other, p51, is a truncated form of p66 that terminates at residue Phe440. Analysis of the HIV-1 protease digest revealed two cleavage sites, at Tyr483-Leu484 and Tyr532-Leu533, in addition to the site at Phe440-Tyr441 that is cleaved to produce p51.
...
PMID:Purification and characterization of heterodimeric human immunodeficiency virus type 1 (HIV-1) reverse transcriptase produced by in vitro processing of p66 with recombinant HIV-1 protease. 137 37

To study the interaction between the primate lentiviruses simian immunodeficiency virus (SIV) and human immunodeficiency virus (HIV) and the CD4 receptor we have cloned and sequenced the CD4 molecule from six non-human primate species: African green monkeys (three subspecies: sabeus, pytherethrus, aethiops), sooty mangabeys, patas monkeys, chimpanzees, rhesus macaques, and pig-tail macaques. Molecular cDNA clones representing CD4 mRNA were generated from total RNA from peripheral blood mononuclear cells (PBMC) by polymerase chain reaction (PCR) amplification including reverse transcriptase in initial reactions followed by two rounds of nested amplifications. Primer sequences were selected from regions conserved among human and rodent CD4 genes. Alignments of deduced amino acid sequences revealed interesting findings. First, all of the primate CD4 molecules were about 90% identical to the human CD4 sequence except the chimpanzee (98%). Second, two macaques or two African green monkey subspecies were as distanly related as the human versus chimpanzee sequences. Third, relatedness of CD4 sequences could not be predicted on the basis of geographic origin (Asian vs. African). Finally, upon sequencing several clones from individual monkeys, a low degree of sequence variation (nucleotide substitutions, deletions, and insertions) was found within the same animal, and in case of sooty mangabeys two distict populations of CD4 molecules were present within three of four individuals. The distinguishing features involved eight amino acid changes, including a single lysine deletion relative to a primate consensus sequence in the first complementary-determing region of V1J1. These two CD4 populations were present also at the genomic DNA level and may arrive from the two chromosomal alleles, suggesting the existence of distinct sooty mangabey subspecies. Overall, the V1J1 and to a lesser extent V2J2 were the most variable regions among the sequences examined. By construction and expression in mammalian cell lines of CD4 chimeras in which these regions of the human CD4 were replaced by those of the African green monkey and pig-tail macaques, a higher molecular mass of the CD4 chimeras were obtained in sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggesting that the additional N-linked glycosylation sites present in these monkey CD4 are also used.
...
PMID:Cloning and sequences of primate CD4 molecules: diversity of the cellular receptor for simian immunodeficiency virus/human immunodeficiency virus. 142 21

The study presents a new in vitro method to investigate the interaction between the glycoprotein (gp)120 of human immunodeficiency virus (HIV) and its receptor, CD4. The method is based on the binding of soluble recombinant CD4 to a human T cell line, 8E5, which constitutively expresses gp120 at its surface as a result of infection with HIV (LAV) and lacks reverse transcriptase activity. The binding of CD4 to gp120 on the cell surface is revealed by immunofluorescence using a murine monoclonal antibody to CD4. Binding can be inhibited by different substances like dextran sulfate, heparin, pentosan polysulfate, but not Leu3a. The reasons for this discrepancy are discussed. We propose this assay as a simple, reproducible, and rapid new method to screen new, pharmacological inhibitors of the gp120/CD4 interaction.
...
PMID:A method to analyze the interaction between gp120 of human immunodeficiency virus and CD4. 147 79


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

---