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)

We have made a computer-assisted search for homology among polymerases or putative polymerases of various viruses and a transposable element, the Drosophila copia-like element 17.6. The search revealed that the putative polymerase (second open reading frame) of the copia-like element 17.6 bears close resemblance in overall structural organization to the pol gene product of Moloney murine leukaemia virus (M-MuLV): they show significant homology to each other at both the N- and C-terminal portions, suggesting that the 17.6 putative polymerase carries two enzymatic activities, related to reverse transcriptase and DNA endonuclease. The putative polymerase of cauliflower mosaic virus (CaMV) shows striking homology with the putative polymerase of 17.6 over almost its entire length, but it lacks the DNA endonuclease-related sequence. Furthermore, it was shown that the N-terminal ends of the M-MuLV pol product and the CaMV and 17.6 putative polymerases exhibit strong sequence homology with the gag-specific protease (p15) of Rous sarcoma virus (RSV) as well as the amino acid sequence predicted from the gag/pol spacer sequence of human adult T-cell leukaemia virus (HTLV). These p15-related sequences contain a highly conserved stretch of amino acids which show a close similarity with sequences around the active site amino acids Asp-Thr-Gly of the acid protease family, suggesting that they have an activity similar to acid protease. On the basis of the alignment of reverse transcriptase-related sequences, a dendrogram representing phylogenetic relationships among all the viruses compared together with 17.6 was constructed and its evolutionary implication is discussed.
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PMID:Close structural resemblance between putative polymerase of a Drosophila transposable genetic element 17.6 and pol gene product of Moloney murine leukaemia virus. 240 86

The NH2-terminal amino acid sequence of Moloney murine leukemia virus reverse transcriptase was determined to be Thr-Leu-Asn-Ile-Glu-Asp-Glu-Tyr-Arg-Leu-His-Glu-. The comparison of the amino acid analysis data obtained after carboxypeptidase Y digestion with the published nucleotide sequence (T. M. Shinnick, R. A. Lerner, and J. G. Sutcliffe, Nature (London) 293, 543-548, 1981) led to the conclusion that the COOH-terminus is Leu coded by CTC in nucleotide positions 4608-4610, and the tentative COOH-terminal sequence is Pro-Asp-Thr-Ser-Thr-Leu-Leu-OH. In light of these and previously reported results the complexity and map order of the pol gene are discussed.
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PMID:Amino- and carboxyl-terminal sequence of Moloney murine leukemia virus reverse transcriptase. 241 14

We have constructed an expression plasmid containing the portion of the Moloney murine leukemia virus genome encoding the reverse transcriptase (RT). When introduced into Escherichia coli this plasmid induces the synthesis of a 70-kDa protein. The RT made in E. coli differs from the viral protein only in that there are two new amino acids, methionine and glycine, substituted for the threonine found at the N terminus of the viral enzyme. Approximately half of the E. coli synthesized RT enzyme is soluble in cell extracts. This protein is active in an RT assay, and like the enzyme purified from virions, is more active in the presence of Mn2+ than Mg2+. We have also constructed a plasmid that induces the synthesis of an RT-integration protein fusion.
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PMID:Expression in Escherichia coli of a Moloney murine leukemia virus reverse transcriptase whose structure closely resembles the viral enzyme. 245 89

Sequences were determined of the coding regions of the M-protein genes of the Glasgow and Orsay strains of vesicular stomatitis virus (Indiana serotype) and of two group III (M-protein) mutants derived from each wild type. Synthetic primers were annealed with viral genomic RNA and extended with reverse transcriptase. The resulting high-molecular-weight cDNA was sequenced directly. Both Glasgow and Orsay wild types differed in 13 bases from a clone of the San Juan strain sequenced by J. K. Rose and C. J. Gallione (J. Virol. 39:519-528, 1981). Six of these base changes caused amino acid changes in each wild type, whereas seven were degenerate. The Orsay and Glasgow sequences resembled each other more closely than either resembled that of Rose and Gallione, differing in eight nucleotides and four amino acids. Each of the four mutants, however, differed from its parent wild type in only one or two point mutations. Every mutation caused a change either from or to a charged amino acid; the change for tsG31 was Lys (position 215) to Glu, the change for tsO23 was Gly (position 21) to Glu, the change for tsO89 was Ala (position 133) to Asp, the changes for tsG33 were Lys (position 204) to Thr and Glu (position 214) to Lys. The charge differences predicted from these amino acid changes was confirmed by nonequilibrium pH gradient electrophoresis for tsG31, tsG33, tsO23, and the two wild types. These mutations affect residues spanning nearly 85% of the linear sequence, although the mutants possess nearly identical phenotypic properties.
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PMID:Sequence alterations in temperature-sensitive M-protein mutants (complementation group III) of vesicular stomatitis virus. 299 21

mRNA for bacteriorhodopsin from Halobacterium halobium has been partially purified. By using this mRNA as template in the presence of reverse transcriptase RNA-dependent DNA nucleotidyltransferase and a 5'-[32P] synthetic oligodeoxyribonucleotide corresponding to amino acids 9-12 of bacteriorhodopsin as primer, we have isolated the major 5'-[32P]cDNA product, approximately 80 nucleotides long, and determined its sequence. Based on the cDNA sequence, the 5'-proximal sequence of bacteriorhodopsin mRNA is G-C-A-U-G-U-U-G-G-A-G-U-U-A-U-U-G-C-C-A-A-C-A-G-C-A-G-U-G-G-A-G-G-G-G-G-U-A-U-C -G-C-A-G-G-C-C-C-A-G-A-U-C-A-C-C-G-G-A-C-G-U-C-C-G. This includes the expected sequence for amino acids 1-8 and shows that bacteriorhodopsin is synthesized as a precursor that is at least 13 amino acids longer (Met-Leu-Glu-Leu-Leu-Pro-Thr-Ala-Val-Glu-Gly-Val-Ser) at the NH2 terminus. Agarose/urea gel electrophoresis of the partially purified mRNA showed several bands; of these, a major one hybridized with 5'-[32P]cDNA. These results suggest that the bacteriorhodopsin mRNA in the partially purified preparation is homogeneous in size and that it constitutes a substantial portion of the RNA preparation subjected to electrophoresis.
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PMID:Bacteriorhodopsin: partial sequence of mRNA provides amino acid sequence in the precursor region. 694 48

A recombinant clone of human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) with reduced sensitivity to 3'-azido-3'-deoxythymidine 5'-triphosphate (AZTTP) and phosphonoformate (PFA), a pyrophosphate analog, has been obtained from the RNA of HTLV-IIIB infected cells using the polymerase chain reaction. The mutant HIV-1 RT retained polymerase activity and was cross-resistant to triphosphate forms of other nucleoside analogs including 2',3'-dideoxycytidine 5'-triphosphate, 2',3'-dideoxyadenosine 5'-triphosphate, and 3'-deoxy-2',3'-didehydrothymidine 5'-triphosphate (D4TTP), but remained sensitive to the non-nucleoside HIV-1 RT inhibitors, such as nevirapine and TIBO R82150. Sequence analysis of the mutant HIV-1 RT revealed a single amino acid substitution (Val-->Ala) at amino acid 90. The substitution of amino acid 90 by the closely related amino acids, such as Thr and Gly, also showed decreased sensitivity to AZTTP, D4TTP, and PFA. All these mutations at amino acid 90 also caused an alteration of Km for thymidine triphosphate. These results suggest that Val at this site plays a role in determining the interaction of the HIV-1 RT enzyme with the pyrophosphate group of deoxynucleoside triphosphate (dNTP) and that the hydrophobicity of the amino acid at this position was the most important determinant in the binding of HIV-1 RT to dNTP.
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PMID:Identification of the amino acid in the human immunodeficiency virus type 1 reverse transcriptase involved in the pyrophosphate binding of antiviral nucleoside triphosphate analogs and phosphonoformate. Implications for multiple drug resistance. 750 27

High level resistance to 3'-azido-3'-deoxythymidine (AZT, zidovudine or Retrovir) is conferred by the presence of four or five mutations (Met-41-->Leu; Asp-67-->Asn; Lys-70-->Arg; Thr-215-->Tyr or Phe; Lys-219-->Gln) in the human immunodeficiency virus (HIV) reverse transcriptase. The order of appearance of these five mutations in asymptomatic patients during therapy has been studied. This has enabled us to propose a model for the acquisition of zidovudine resistance mutations during the treatment of high-risk asymptomatic HIV-infected individuals. A consistent acquisition pattern of mutations at codons 41, 70 and 215 was observed in 17 individuals. Complex mixtures of HIV species containing different combinations of single and linked double resistance mutations were present early in zidovudine therapy in isolates from two patients studied in detail. From these mixtures the linked Leu-41/Tyr-215 genotype outgrew all others initially. The development of each new virus population is likely to be mediated primarily by the increase in the level of drug resistance rather than changes in the growth kinetics of the virus. This leads us to conclude that one major driving force in the outgrowth of different mutant viruses is the selective advantage conferred by higher levels of drug resistance.
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PMID:Zidovudine treatment results in the selection of human immunodeficiency virus type 1 variants whose genotypes confer increasing levels of drug resistance. 750 70

Mutation in the human immunodeficiency virus type 1 reverse transcriptase (RT) at codon 215 has been shown to play a significant role in resistance to zidovudine (AZT). Substitution of threonine with tyrosine or phenylalanine alone confers decreased susceptibility to the inhibitor. In this study we constructed a panel of 10 viruses with different amino acids at this codon, including 7 novel mutants, and assessed their susceptibilities to AZT. The majority of the new mutants were AZT sensitive, whereas the Thr-215-->Trp mutant was partially resistant (threefold less susceptible). A combination of the Thr-215-->Trp with the other AZT resistance mutations Lys-70-->Arg and Met-41-->Leu gave additive resistance. The Thr-215-->Phe virus was less AZT resistant than the Thr-215-->Tyr mutant, both on its own and when each was combined with the Met-41-->Leu mutant. These observations confirm the general hypothesis that increased bulk of the amino acid side chains at this position confers decreased AZT sensitivity. A leucine-to-valine substitution at codon 74 has previously been found to confer dideoxynucleoside resistance. We constructed mutants with five novel amino acid substitutions (Ala, Gly, Glu, Met, and Asp) at codon 74. Of these, only one (that with the Met substitution) retained enough RT activity to yield viable virus. It thus appears that there are severe structure-function constraints on the amino acid side chains at this position in the enzyme. The activities of the Leu-74-->Ala and Leu-74-->Met RT enzymes expressed in Escherichia coli appeared to have reduced susceptibility to ddGTP compared with the wild-type enzyme. The mutants described in this work may prove useful for correlation with structural studies of the human immunodeficiency virus type 1 RT.
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PMID:Mutagenic study of codons 74 and 215 of the human immunodeficiency virus type 1 reverse transcriptase, which are significant in nucleoside analog resistance. 751 65

We generated variants of the human immunodeficiency virus type 1 (HIV-1) that are resistant to 2',3'-dideoxycytidine (ddC) and 2',3'-didehydro-3'-deoxythymidine (d4T) by in vitro selection in MT-4 cells. Portions of flanking protease and integrase sequences as well as the complete reverse transcriptase (RT) open-reading frame of these viruses were cloned and sequenced, using polymerase chain reaction (PCR)-based methods. Mutations were observed at amino acid position 65 (Lys-->Arg; AAA-->AGA) when ddC was employed in the selection procedure and at site 50 (Ile-->Thr; ATT-->ACT) when d4T was used. We confirmed the ability of these mutations to confer diminished sensitivity for these compounds by site-directed mutagenesis, in which these mutations were inserted into the pol gene of infectious recombinant HXB2-D DNA. Viruses that contained the site 65 mutation possessed approximately 5-10 fold resistance against ddC when compared with wild-type HXB2-D. The site 50 mutation conferred approximately 30-fold resistance to d4T in these same assays. Similar results were obtained using primary cord blood lymphocytes in drug resistance assays, indicating that these mutations could confer drug resistance in more than one cell type and that the respective mutations could be expressed in cells of primary origin. No cross-resistance against 3'-azido-3'-deoxythymidine (AZT) was noted for either the site 65 or 50 mutations.
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PMID:Identification of novel mutations that confer drug resistance in the human immunodeficiency virus polymerase gene. 751 78

We have selected a human immunodeficiency virus type 1 (HIV-1) mutant strain with a moderate (sevenfold) level of resistance to the nucleoside analog 2',3'-didehydro-2',3'-dideoxythymidine (D4T or stavudine). After serial passage of the HXB2 strain of HIV-1 in MT4 cells, a novel mutation involving two nucleotide substitutions in codon 75 of the viral reverse transcriptase, altering valine to threonine, was seen. When introduced into a wild-type HIV-1 background by site-directed mutagenesis, the T-75 mutation conferred cross-resistance to the dideoxynucleosides dideoxyinosine and dideoxycytosine as well as to 2',3'-didehydro-2',3'-dideoxycytosine.
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PMID:Novel mutation (V75T) in human immunodeficiency virus type 1 reverse transcriptase confers resistance to 2',3'-didehydro-2',3'-dideoxythymidine in cell culture. 752 29


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