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)

We have studied selected mutants of human immunodeficiency virus type 2 (HIV-2) reverse transcriptase (RT) in a cell-free system in order to assess whether the mutant proteins exhibit a reduction in the sensitivity to nucleoside analog inhibitors similar to that of HIV-1 RT. We have modified, by site-directed mutagenesis, several of those amino acid residues so that their equivalent substitutions in HIV-1 RT have led to the formation of HIV-1 RT variants with the highest degree of resistance to dideoxynucleoside triphosphates (i.e., Glu-89-->Gly, Leu-74-->Val, and Ser-215-->Tyr [which is comparable to the Thr-215-->Tyr mutation of HIV-1 RT] and the double mutations Glu-89-->Gly/Ser-215-->Tyr and and Leu-74-->Val/Ser-215-->Tyr). The similarity found between resistance of the newly generated HIV-2 RT mutants to nucleoside analogs and that of the comparable mutants of HIV-1 RT can support the notion that the overall protein folding around the DNA polymerase active site in HIV-2 RT is quite similar to that of HIV-1 RT.
...
PMID:Resistance to nucleoside analogs of selective mutants of human immunodeficiency virus type 2 reverse transcriptase. 752 86

Five structurally related thiophene and furane analogues of the oxathiin carboxanilide derivative NSC 615985 (UC84) (designated UC10, UC68, UC81, UC42, and UC16) were identified as potent inhibitors of HIV-1 replication in cell culture and HIV-1 reverse transcriptase activity. These compounds were markedly active against a series of mutant HIV-1 strains, containing the Leu-100-->Ile, Val-106-->Ala, Glu-138-->Lys, or Tyr-181-->Cys mutations in their reverse transcriptase. However, the thiocarboxanilide derivatives selected for mutations at amino acid positions 100 (Leu-->Ile), 101 (Lys-->Ile/Glu), 103 (Lys-->Thr/Asp) and 141 (Gly-->Glu) in the HIV-1 reverse transcriptase. The compounds completely suppressed HIV-1 replication and prevented the emergence of resistant virus strains when used at 1.3-6.6 microM--that is, 10- to 25-fold lower than the concentration required for nevirapine and bis(heteroaryl)piperazine (BHAP) U90152 to do so. If UC42 was combined with the [2',5'-bis-O-(tert-butyldimethylsilyl)-3'-spiro-5"-(4"-amino-1",2"- oxathiole-2",2"-dioxide)]-beta-D-pentofuranosyl (TSAO) derivative of N3-methylthymine (TSAO-m3T), virus breakthrough could be prevented for a much longer time, and at much lower concentrations, than if the compounds were used individually. Virus breakthrough could be suppressed for even longer, and at lower drug concentrations, if BHAP was added to the combination of UC42 with TSAO-m3T, which points to the feasibility of two- or three-drug combinations in preventing virus breakthrough and resistance development.
...
PMID:Suppression of the breakthrough of human immunodeficiency virus type 1 (HIV-1) in cell culture by thiocarboxanilide derivatives when used individually or in combination with other HIV-1-specific inhibitors (i.e., TSAO derivatives). 753 17

Foscarnet (phosphonoformic acid) is a pyrophosphate analog that inhibits the replication of human immunodeficiency virus type 1 (HIV-1) in vitro and in patients with AIDS. HIV-1 resistance to foscarnet has not been reported despite long-term foscarnet therapy of AIDS patients with cytomegalovirus disease. We therefore attempted to select foscarnet-resistant HIV-1 in vitro by serial endpoint passage of virus in 400 microM foscarnet. After 13 cycles of passage in MT-2 cells, virus exhibiting > or = 8.5-fold foscarnet resistance was isolated. The reverse transcriptase (RT) from resistant virions exhibited a similar level of foscarnet resistance in enzyme inhibition assays (approximately 10-fold resistance). Foscarnet-resistant virus showed increased susceptibility to 3'-azido-3'-deoxythymidine (90-fold) and to the HIV-1-specific RT inhibitors TIBO R82150 (30-fold) and nevirapine (20-fold). DNA sequence analysis of RT clones from resistant virus revealed the coexistence of two mutations in all clones: Gln-161 to Leu (CAA to CTA) and His-208 to Tyr (CAT to TAT). Sequence analysis of six clinical HIV-1 isolates showing reduced susceptibility to foscarnet revealed the Tyr-208 mutation in two, the Leu-161 mutation in one, and a Trp-88-to-Ser or -Gly mutation in four isolates. Site-specific mutagenesis and production of mutant recombinant viruses demonstrated that the Leu-161, Ser-88, and Tyr-208 mutations reduced HIV-1 susceptibility to foscarnet 10.5-, 4.3-, and 2.4-fold, respectively, in MT-2 cells. In the crystal structure of HIV-1 RT, the Gln-161 residue lies in the alpha E helix beneath the putative deoxynucleoside triphosphate (dNTP) binding site. The Gln-161-to-Leu mutation may affect the structure of the dNTP binding site and its affinity for foscarnet. The location of the Trp-88 residue in the Beta5a strand of HIV-1 RT suggest that the Ser-88 mutation affects template-primer binding, as do several mutations that affect RT susceptibility to nucleoside analogs.
...
PMID:Novel mutations in reverse transcriptase of human immunodeficiency virus type 1 reduce susceptibility to foscarnet in laboratory and clinical isolates. 754 60

The retrovirus protease (PR), an aspartic PR, is composed of two identical subunits, each containing a conserved tripeptide sequence present at the active site of the enzyme. Asp-Ser-Gly is found in avian sarcoma leukaemia viruses (ASLV) and Asp-Thr-Gly in mammalian oncoretroviruses. We have mutated the conserved sequence at the active site of ASLV PR by converting the Ser and Gly residues to Thr and Ala, respectively. Replacement of Gly with Ala yielded an ASLV PR devoid of proteolytic activity. The Ser to Thr conversion did not alter the substrate specificity of the enzyme. Both wild-type and mutated PRs correctly cleaved viral precursors expressed in bacterial cells, as well as synthetic peptides homologous to ASLV and human immunodeficiency virus type 1 cleavage sites. Bacterially produced ASLV PR with Thr instead of Ser had increased enzymatic activity, as shown by hydrolysis of synthetic peptides. However, this mutation reduced the production of reverse transcriptase-containing particles and infectious virus following transfection of permissive cells with virus DNA.
...
PMID:Point mutation in avian sarcoma leukaemia virus protease which increases its activity but impairs infectious virus production. 754 58

Nevirapine is a highly potent and specific inhibitor of human immunodeficiency virus type 1 (HIV-1) polymerase, but is inactive against HIV-2 and other polymerase. Previous studies demonstrated that residues 176-190 of HIV-1 reverse transcriptase (RT) can confer nevirapine sensitivity to HIV-2 RT. To better characterize the role of this sequence in HIV-1 RT, we have progressively substituted residues 176-190 of HIV-2 RT for those of HIV-1 RT and monitored the impact on the kinetic properties; inhibitory activity of nevirapine (11-cyclopropyl-5,11-dihydro-4-methyl-6H-dipyrido[2,3-b:2',3'-e] [1,4]diazepin-6-one), E-BPU (5-ethyl-1-benzyloxymethyl-6-(phenylthio)-uracil), and TIBO-R82150 ((+)-S-4,5,6,7-tetrahydro-5-methyl-6-(3-methyl-2-butenyl)imidazo[4,5,1-j k] [1,4]benzodiazepin-2(1H)-thione); and inhibitor-induced fluorescence changes of the mutant enzymes. The study revealed that in addition to Try-181 and Tyr-188, a new amino acid residue (Gly-190) plays an important role in determining susceptibility to nevirapine and E-BPU, but not to TIBO-R82150. These data argue that these non-nucleoside inhibitors fit differently, even though they share a common binding pocket. Nevirapine was seen to exert inhibitory activity by altering the interaction of the enzyme with the template-primer. Kinetic parameters were modulated by the template (DNA versus RNA) as well as by some of the mutations.
...
PMID:Amino acid substitutions in HIV-1 reverse transcriptase with corresponding residues from HIV-2. Effect on kinetic constants and inhibition by non-nucleoside analogs. 768 67

We have reported previously mitogenic effects of gastrin on several immortalized and neoplastic cell lines, including Swiss 3T3 fibroblasts. Receptor subtypes, cholecystokinin (CCK)-A and CCK-B, for a closely related peptide, cholecystokinin, were recently cloned. These studies were undertaken to investigate if CCK-A- and CCK-B receptors were perhaps mediating the mitogenic effects of gastrin on Swiss 3T3 cells. Receptor antagonists that inhibit the biological effects and binding of peptides to the CCK-A (L-364,718 (L18)) and CCK-B (L-365,260 (L60)) receptors were ineffective toward inhibiting the binding and proliferative effects of gastrin on Swiss 3T3 cells. Radiolabeled L18 and L60 demonstrated no binding to the cells, indicating that CCK-A and CCK-B receptors may be absent on Swiss 3T3 cells. Radiolabeled CCK-8, gastrin, L18, and L60, on the other hand, demonstrated specific binding to a pancreatic cancer cell line (AR42J cells) (used as a positive control). In cross-linking studies the molecular mass of the major band of gastrin receptors (GR) on Swiss 3T3 cells was determined to be approximately 45 kDa. The mitogenic potency of 0.1-1.0 nM gastrin-like peptides on Swiss 3T3 cells was in the order of G1-17 > or = G1-17-Gly > G5-17 > or = G5-17-Gly > G2-17 > CCK-8-Gly > or = G1-17-Lys > or = CCK-8. The relative binding affinity of the peptides (based on the dose-dependent inhibition of binding of 125I-G1-17 to Swiss 3T3 cells) was similar to the relative mitogenic potency of the peptides as given above. Furthermore, G1-17-Gly was equally effective as G1-17 in displacing the binding of 125I-G1-17 to the 45-kDa GR from the Swiss 3T3 cells. Based on these studies it became evident that the novel gastrin preferring GR, expressed by Swiss 3T3 cells, binds and mediates the mitogenic effects of not only the mature (amidated) forms of gastrin-like peptides but also binds and mediates the mitogenic effects of glycine-extended forms of gastrin-like peptides. Possible mRNA expression of CCK-A and CCK-B receptor subtypes by gastrin-responsive rodent intestinal and fibroblast cell lines (Swiss 3T3, IEC-6, CA) was measured by the methods of Northern blot analysis and reverse transcriptase-polymerase chain reaction. mRNA from rat pancreas, AR42J cells, and rat antrum served as positive controls.(ABSTRACT TRUNCATED AT 400 WORDS)
...
PMID:Novel gastrin receptors mediate mitogenic effects of gastrin and processing intermediates of gastrin on Swiss 3T3 fibroblasts. Absence of detectable cholecystokinin (CCK)-A and CCK-B receptors. 772 37

Complementary DNA fragments encoding the prepro-salmon gonadotropin-releasing hormone ([Trp7, Leu8]GnRH, sGnRH) of the red seabream Pagrus major were amplified from mRNA of the olfactory bulbs using a reverse transcriptase-polymerase chain reaction (RT-PCR), and the full-length cDNA was cloned from a cDNA library using the PCR-amplified cDNA as a probe. The cDNA consisted of 442 bp, including an open reading frame of 270 bp which encoded the prepro-sGnRH (90 amino acid residues). The prepro-sGnRH had the same architecture as that reported in other species. It was composed of a signal peptide, sGnRH and a GnRH-associated peptide (GAP), which was connected to sGnRH by a Gly-Lys-Arg sequence. The prepro-sGnRH of the red seabream had 90% amino acid identity to the prepro-sGnRH from an African cichlid Haplochromis burtoni which belongs to the same suborder as the red seabream; however, identity was lower to the prepro-sGnRH from Atlantic salmon Salmo salar (74%) and masu salmon Oncorhynchus masou (70%). The GnRH peptide itself and the Gly-Lys-Arg sequence in the prepro-GnRH are highly conserved among vertebrates. The red seabream GAP also shows significant amino acid identity to the GAPs of the African cichlid (89%), Atlantic salmon (74%), and masu salmon (67%), but exhibits no significant identity to chicken or mammalian GAP.
...
PMID:Molecular cloning of a cDNA encoding the prepro-salmon gonadotropin-releasing hormone of the red seabream. 785 23

Manganese superoxide dismutase (MnSOD)-encoding cDNAs from multiple mouse organs, including liver, kidney, brain, spleen and heart, show three sequence differences compared with the previously published mouse placenta MnSOD cDNA. The differences cause substitutions of Val(-7)-->Gly (GTG-->GGT) and Met(114)-->Val (ATG-->GTG) and a G746 deletion in the 3' untranslated region. The analysis, by reverse transcriptase-polymerase chain reaction-direct sequencing, of BALB/c mouse placenta RNA revealed the same sequence in the placenta MnSOD as that from multiple mouse organs. The data presented will be useful for wild-type sequence verification and possible point mutation detection.
...
PMID:Sequence of manganese superoxide dismutase-encoding cDNAs from multiple mouse organs. 840 27

A large variety of carboxanilide derivates in which the original oxathiin moiety present in the prototype compound UC84 was replaced by a non-cyclic lipophilic entity has been evaluated for their inhibitory effect against wild-type human immunodeficiency virus type 1 (HIV-1/IIIB) and several mutant viruses derived thereof (i.e. HIV-1/138-Lys, HIV-1/181-Cys, HIV-1/106-Ala and HIV-1/100-IIe). Isopropoxy was the most favorable substituent resulting in molecules that were markedly inhibitory to the wild-type (EC50 0.004-0.04 microgram/ml) as well as the mutant HIV-1 strains (EC50 0.06-0.75 microgram/ml). In this respect, they proved superior to several other HIV-1-specific non-nucleoside reverse transcriptase inhibitors (NNRTIs) that are currently the subject of clinical trials. One of the most potent HIV-1 inhibitors among the thiocarboxanilide derivatives, namely UC38, selected for a mutant virus strain in which Lys at position 101 and Gly at position 190 of the reverse transcriptase was replaced by Glu.
...
PMID:Activity of various thiocarboxanilide derivatives against wild-type and several mutant human immunodeficiency virus type 1 strains. 854 Jul 45

Osteogenesis imperfecta (OI) is a heritable connective tissue disorder characterized by bone fragility. Most cases of severe OI result from mutations in the coding region of the COL1A1 or COL1A2 genes yielding an abnormal collagen alpha chain. In contrast, many patients with mild OI show evidence of a null allele due to a premature stop mutation in the mutant RNA transcript. We have previously described a null allele arising from a splice donor mutation where the transcript containing the included intron was sequestered in the nucleus. Here we demonstrate that transcripts from null alleles arising from premature stop mutations are also present in the nucleus and absent in the cytoplasm. Using reverse transcriptase-PCR and single-strand conformational polymorphism of COL1A1 mRNA from patients with mild OI, we describe three patients with distinct null producing mutations identified from the mutant transcript within the nuclear compartment. A fourth patient with a Gly--->Arg expressed point mutation exhibits the mutant transcript in both compartments. Defining the distribution of allelic variants of COL1A1 mRNA in the nuclear and cytoplasmic compartments gives further insight into cell biology of OI and provides a strategy for investigating potential causes of a null allele.
...
PMID:Nuclear retention of COL1A1 messenger RNA identifies null alleles causing mild osteogenesis imperfecta. 861 26


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

---