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 conformation of the last 201 nucleotides located at the 3'-end of brome mosaic virus (BMV) RNAs was investigated in solution using different chemical and enzymatic probes. Bases were probed with dimethylsulfate (which methylates N-1 positions of A, N-3 positions of C and N-7 positions of G), a carbodiimide (which modifies N-1 positions of G and N-3 positions of U) and diethylpyrocarbonate (which modifies N-7 positions of A). Ribonucleases T1, U2 and S1 were used to map unpaired nucleotides and ribonuclease V1 to monitor paired bases or stacked nucleotides. Cleavage or modification sites were detected by gel electrophoresis either indirectly by analyzing DNA sequence patterns generated by primer extension with reverse transcriptase of the modified RNAs or by direct identification within the statistical cleavage patterns of the RNA. On the basis of these biochemical results, an atomic model was built by computer modeling and its stereochemistry refined. The deduced secondary structure of the RNA confirms data previously proposed by others but contains additional base-pairs (A27-U32, A28-G31, G41-A134, G64-C68, U80-A99, G81-A98, G88-U91, G100-U126, U104-U125, G162-G166 and A172-A191), one new tertiary long-range interaction (U103-U164) and a small triple helical conformation with (G41-A134)-A18 and (C42-G133)-A17 interactions. The new secondary structure also indicates the existence of a second pseudoknot involving pairing between residues A181 to A184 and residues U197 to U194, outside the domain conferring tyrosylation ability to BMV RNA. The main outcome from the model stems from its intricate folding, which allows a new assignment for the domains mimicking the anticodon- and D-loop regions of tRNA. Interestingly, the stem and loop region found structurally to be analogous to the anticodon arm of tRNA(Tyr) does not contain the tyrosine anticodon involved in the aminoacylation process. The structural analogies with canonical tRNA(Tyr) illustrate the functional mimicry existing between the BMV RNA structure and canonical tRNA(Tyr) that allows for their efficient aminoacylation by tyrosyl-tRNA synthetase. This structural model rationalizes mutagenic and footprinting data that have established the importance of specific regions of the viral RNA for recognition by its replicase, (ATP,CTP):tRNA nucleotidyl-transferase and yeast tyrosyl-tRNA synthetase. The new fold has biological implications that can be used as a predictive tool for elaborating new experiments.
...
PMID:Solution structure of the 3'-end of brome mosaic virus genomic RNAs. Conformational mimicry with canonical tRNAs. 828 79

To determine the expression of various protein-tyrosine phosphatases (PTPs) in human gastric cancers, cDNAs encoding conserved PTP domains were amplified by reverse transcriptase polymerase chain reaction from KATO-III cell mRNA and sequenced. Among 72 polymerase chain reaction clones, one of the cDNA sequences encoded a novel potential PTP (stomach cancer-associated PTP, SAP-1). The full length (3.9 kilobases) of the SAP-1 cDNA was further isolated from the KATO-III cell cDNA library and the WiDr cell cDNA library. The predicted amino acid sequence of the SAP-1 cDNA showed that mature SAP-1 consisted of 1093 amino acids and a transmembrane-type PTP, which possessed a single PTP-conserved domain in the cytoplasmic region. The extracellular region of SAP-1 consisted of eight fibronectin type III-like structure repeats and contained multiple N-glycosylation sites. These data suggest that SAP-1 is structurally similar to HPTP beta and that SAP-1 and HPTP beta represent a subfamily of transmembrane-type PTPs. SAP-1 was mainly expressed in brain and liver and at a lower level in heart and stomach as a 4.2-kilobase mRNA, but it was not detected in pancreas or colon. In contrast, among cancer cell lines tested, SAP-1 was highly expressed in pancreatic and colorectal cancer cells. The bacterially expressed SAP-1 fusion protein had tyrosine-specific phosphatase activity. Immunoblotting with anti-SAP-1 antibody showed that SAP-1 is a 200-kDa protein. In addition, transient transfection of SAP-1 cDNA to COS cells resulted in the predominant expression of a 200-kDa protein recognized by anti-SAP-1 antibody. SAP-1 is mapped to chromosome 19 region q13.4 and might be related to carcinoembryonic antigen mapped to 19q13.2.
...
PMID:Molecular cloning of a human transmembrane-type protein tyrosine phosphatase and its expression in gastrointestinal cancers. 829 59

Suramin has long been used for the treatment of Gambian and Rhodesian trypanosomiasis and oncocerciasis. More recently, the demonstration that suramin inhibits DNA polymerases, reverse transcriptase and the lymphocyte terminal deoxynucleotidyl transferase has led to its clinical trials for the treatment of AIDS and cancer. The precise nature of suramin's anti-neoplastic action is not clear at this time. Suramin rapidly alters the tyrosine-specific phosphorylation of cellular proteins in many cancer cell lines. Here we demonstrate that suramin strongly inhibits the activity of CD45, the principal tyrosine specific protein phosphatase of T lymphocytes. Suramin-induced inactivation of CD45 is noncompetitive, irreversible and complete within 10 min. The ability of suramin to block CD45 mediated phosphatase function provides both new insight into the mechanism of action of this agent and a useful new probe for studies of T cell activation.
...
PMID:Suramin, an experimental chemotherapeutic drug, irreversibly blocks T cell CD45-protein tyrosine phosphatase in vitro. 833 52

The insulin receptor possesses tyrosine kinase activity which is thought to mediate the biological effects of insulin upon target cells. pp120 is a liver-specific glycoprotein of apparent molecular size of 120 kDa that is phosphorylated on tyrosine residues by the receptors for insulin, insulin-like growth factor-I, and epidermal growth factor. Previously, we demonstrated that pp120 is identical to a liver-specific ecto-ATPase. In the present study, we have cloned the rat gene encoding pp120/ecto-ATPase. The gene is contained within approximately 15 kilobases of genomic DNA, and consists of nine exons interrupted by eight introns. Using the reverse transcriptase/polymerase chain reaction, we isolated cDNA clones complementary to rat liver mRNA encoding pp120/ecto-ATPase. Sequence analysis indicated the presence of two populations of cDNA's that differ by the presence or absence of a 53-base pair (bp) fragment encoding the juxta-membrane region of the cytoplasmic domain. By cloning the corresponding region of the ecto-ATPase gene, we demonstrated that the 53-bp represents exon 7 of the gene. This 53-bp exon undergoes alternative splicing, thereby giving rise to two mRNA variants. Deletion of this 53-bp cassette exon introduces a frameshift, and results in a premature chain termination codon that truncates the cytoplasmic domain. The truncated cytoplasmic domain contains 10 rather than 71 amino acid residues. Because the short isoform of ecto-ATPase lacks the putative sites for tyrosine- and serine-specific phosphorylation, this alternative splicing may have a major effect upon the physiological function of the enzyme.
...
PMID:pp120/ecto-ATPase, an endogenous substrate of the insulin receptor tyrosine kinase, is expressed as two variably spliced isoforms. 838 Apr 6

N-terminal amino acid sequencing, ion spray mass spectrometry, and cleavage of synthetic peptide substrates were used to identify the N and C termini of the mature Gag and Pol proteins of feline immunodeficiency virus (FIV). The Gag polyprotein encodes matrix (MA), capsid (CA), and nucleocapsid (NC) proteins. The Gag-Pol polyprotein encodes, in addition to the above proteins, protease (PR), reverse transcriptase (RT), dUTPase (DU), and integrase (IN). Secondary cleavage of RT at Trp-595-Tyr-596 of Pol yields a truncated form lacking the C-terminal RNase H domain. The observed and expected molecular masses of the viral proteins were in agreement, with three exceptions. (i) The molecular mass of MA was 14,735 Da, compared with a predicted mass of 14,649 Da, based on a single cleavage at Tyr-135-Pro-136 of Gag. The observed molecular mass is consistent with myristoylation of MA, which was confirmed by metabolic labeling of FIV MA with [3H]myristic acid. (ii) The N terminus of the NC protein is generated via cleavage at Gln-366-Val-367 of Gag, which predicts a mass of 25,523 for CA and 9,101 for the major form of NC. The observed mass of CA was 24,569, consistent with loss of nine C-terminal amino acids by a second cleavage of CA at Leu-357-Leu-358. Synthetic FIV protease accurately cleaved synthetic peptide substrates containing this site. (iii) The actual mass of NC (7,120 Da) was approximately 2 kDa smaller than the mass predicted by synthesis to the stop codon at the end of Gag (9,101 Da). Experiments are in progress to characterize additional cleavage(s) in NC.
...
PMID:Identification of proteolytic processing sites within the Gag and Pol polyproteins of feline immunodeficiency virus. 838 14

The feline lentivirus, FIV, contains dUTPase (DU) as part of the enzyme cassette encoded by the viral pol gene (Elder et al., 1992, J. Virol. 66, 1791-1794). The enzyme is processed from the Pol polyprotein and is packaged into infectious virions. We report here the basic characteristics of the viral enzyme, including substrate specificity, ion requirements, and pH optimum. We also report the overexpression of DU in Escherichia coli and insertional mutagenesis of the enzyme in the context of the complete provirus or DU alone. The enzyme requires Mg2+ for full activity and competition studies employing unlabeled dNTPs indicated that DU has an absolute preference for dUTP. The pH optimum for FIV DU is pH 7.0. The limits of the protein dictate a species of M(r) 14,350, which agrees precisely with the determination by ion spray mass spectroscopy of DU isolated from virions. Cleavage sites at the junctions between DU, RT, and IN, as defined by N-terminal amino acid sequencing of each protein species, are consistent with predictions for sites of cleavage by aspartate protease. In-frame insertional mutagenesis at Tyr 75 of DU abolishes activity. Cells transfected with proviruses containing this mutation express virion-associated reverse transcriptase activity but lack DU activity. The resultant virions replicate slower than those possessing wild-type DU. Tests are currently underway to evaluate the consequences of DU mutagenesis on in vivo phenotype.
...
PMID:Molecular cloning and characterization of deoxyuridine triphosphatase from feline immunodeficiency virus (FIV). 839 97

Halogenated gomisin J (a derivative of lignan compound), represented by the bromine derivative 1506 [(6R, 7S, S-biar)-4,9-dibromo-3,10-dihydroxy-1,2,11,12-tetramethoxy-6, 7-dimethyl-5,6,7,8- tetrahydrodibenzo[a,c]cyclo-octene], was found to be a potent inhibitor of the cytopathic effects of human immunodeficiency virus type 1 (HIV-1) on MT-4 human T cells (50% effective dose, 0.1 to 0.5 microM). Gomisin J derivatives were active in preventing p24 production from acutely HIV-1-infected H9 cells. The selective indices (toxic dose/effective dose) of these compounds were as high as > 300 in some systems. 1506 was active against 3'-azido-3'-deoxythymidine-resistant HIV-1 and acted synergistically with AZT and 2',3'-ddC. 1506 inhibited HIV-1 reverse transcriptase (RT) in vitro but not HIV-1 protease. From the time-of-addition experiment, 1506 was found to inhibit the early phase of the HIV life cycle. A 1506-resistant HIV mutant was selected and shown to possess a mutation within the RT-coding region (at position 188 [Tyr to Leu]). The mutant RT expressed in Escherichia coli was resistant to 1506 in the in vitro RT assay. Some of the HIV strains resistant to other nonnucleoside HIV-1 RT inhibitors were also resistant to 1506. Comparison of various gomisin J derivatives with gomisin J showed that iodine, bromine, and chlorine in the fourth and ninth positions increased RT inhibitory activity as well as cytoprotective activity.
...
PMID:Anti-human immunodeficiency virus (HIV) activities of halogenated gomisin J derivatives, new nonnucleoside inhibitors of HIV type 1 reverse transcriptase. 854 Jul 6

The parameters governing the polymerization mechanism of reverse transcriptase containing the tyrosine to cysteine mutation at position 181 (Y181C) were determined using pre-steady-state techniques. The pathway for single nucleotide incorporation catalyzed by Y181C is similar to that determined for wild-type RT where a rate-limiting conformational change precedes fast chemistry and is followed by slow steady-state release of the primer/template. The Y181C mutant enzyme binds a 25/45-mer duplex DNA tightly with a Kd of 11 nM. However, the Y181C mutation weakens the nucleotide affinity 2-3-fold relative to the wild-type complex. We also determined the parameters governing the mechanism of nonnucleoside inhibitor resistance with Y181C. The Kd value of Nevirapine with the mutant E.DNA complex increased approximately 500-fold. The decreased affinity of Nevirapine for the mutant enzyme is a consequence of a faster inhibitor dissociation rate from the enzyme complex of Y181C relative to that of the wild-type. The E.DNA complex of Y181C may be saturated with Nevirapine, and the I.E.DNA complex is capable of a maximum incorporation rate of 0.1 s-1 (a 10-fold faster rate than that of the wild-type I.E.DNA complex). The overall two-step binding of nucleotide to Y181C in the presence of Nevirapine remains unaffected.
...
PMID:HIV-1 reverse transcriptase resistance to nonnucleoside inhibitors. 854 41

Eph and its homologues form the largest subfamily of receptor tyrosine kinases. Normal expression patterns of this subfamily indicate roles in differentiation and development, whereas their overexpression has been linked to oncogenesis. This study investigated the potential role of Eph-related molecules during very early embryonic development by examining their expression in embryonic stem (ES) cells and embryoid bodies differentiated from ES cells in vitro. By use of a strategy based on reverse transcriptase-mediated PCR, nine clones containing Eph-subfamily sequence were isolated from ES cells. Of these, eight were almost identical to one of four previously identified molecules (Sek, Nuk, Eck, and Mek4). However, one clone contained sequence from a novel Eph-subfamily member, which was termed embryonic stem-cell kinase or Esk. Northern analysis showed expression of Esk in ES cells, embryoid bodies, day 12 mouse embryos, and some tissues of the adult animal. Levels of expression were similar in ES cells and embryoid bodies. By comparison, Mek4 showed no significant transcription in the ES cell cultures by Northern analysis, whereas Eck displayed stronger signals in ES cells than in the embryoid bodies. These results suggest that Eph-subfamily molecules may play roles during the earliest phases of embryogenesis. Furthermore, the relative importance of different members of this subfamily appears to change as development proceeds.
...
PMID:Embryonic stem cells express multiple Eph-subfamily receptor tyrosine kinases. 855 93

UC 38, a simple analog of oxathiin carboxanilide, UC 84, lacking the oxathiin ring, was found to be a potent inhibitor of human immunodeficiency virus (HIV)-1-induced cell killing and HIV replication in a variety of human cell lines, as well as in human peripheral blood lymphocytes and macrophages. UC 38 was active against a wide range of biologically diverse laboratory and clinical strains of HIV-1. However, UC 38 was inactive against HIV-2 and both nevirapine- and pyridinone-resistant strains of HIV-1. UC 38 selectively inhibited HIV-1 reverse transcriptase (RT), but not HIV-2 RT. Combination of UC 38 with 3'-azido-3'-deoxythymidine synergistically inhibited HIV-induced cell killing. An HIV-1 isolate resistant to UC 38 was selected in cell culture, and the mutations in the RT nucleotide sequences were determined. Comparison with the wild-type RT sequence revealed an amino acid change at position 181 (Tyr to Cys). The UC 38-resistant virus was found to be cross-resistant to a variety of structurally diverse non-nucleoside RT inhibitors. UC 38 was susceptible to rapid degradation in vitro and in vivo; yet, nontoxic in vivo concentrations of UC 38 many-fold in excess of the in vitro effective concentrations could be achieved and maintained after s.c. or p.o. administration in hamsters. These results establish UC 38 as a new chemotype within the general class of HIV-1-specific RT inhibitors. The favorable physical characteristics, lack of toxicity, potency and bioavailability of UC 38 may make it a candidate for combination chemotherapy of acquired immune deficiency syndrome.
...
PMID:Biological and biochemical anti-human immunodeficiency virus activity of UC 38, a new non-nucleoside reverse transcriptase inhibitor. 855 46


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

---