Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The interactions between the Reverse Transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) and the natural tRNA(Lys3) primer for initiation of viral DNA synthesis were examined. We constructed a set of HIV-1 RNA templates in which the wild-type primer binding site (PBS(Lys3)) is replaced by sequences complementary to tRNA(lle), tRNA(Lys1,2), tRNA(Phe), tRNA(Pro) or tRNA(Trp) and tested the ability of RT enzymes of different retroviral species to initiate cDNA synthesis from self versus non-self tRNA primers. We demonstrate that initiation of HIV-1 reverse transcription is a specific process that is most efficient with the self tRNA(Lys3) primer. Interestingly, the property of HIV-1 RT to discriminate against non-self tRNA primers is lost upon extension of the tRNA by only two deoxyribonucleotides. Furthermore, selective tRNA priming by HIV-1 RT was not observed with viral RNA-tRNA(Lys3) duplexes isolated from HIV-1 virion particles, suggesting that the majority of tRNA(Lys3) primers annealed to viral RNA in particles is extended by a variable number of deoxyribonucleotides. This result indicates that reverse transcription is initiated relatively early in nascently assembled virions.
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PMID:HIV-1 reverse transcriptase discriminates against non-self tRNA primers. 895 74

Activation of human blood neutrophils and monocytes for enhanced release of toxic oxygen radicals may take place after priming with several cytokines including hematopoietic growth factors. The potential impact of human immunodeficiency virus (HIV) on this response and the relative potency of various cytokines remains unclear. Blood neutrophils and monocytes were isolated from 25 HIV outpatients with variable immunodeficiency. Oxidative burst response upon stimulation with N-formyl-methionyl-leucyl-phenylalanine was assessed in neutrophils after priming with granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF) and interferon-gamma (IFN-g), and in monocytes after priming with GM-CSF and IFN-g. Monocyte oxidative burst responses were not changed in patients or controls. In contrast, following priming with IFN-g, GM-CSF or medium (but not G-CSF) the neutrophils in HIV patients with CD4 counts > 200 x 10(9)/L exhibited a significantly higher chemiluminescence response than was seen in healthy age-matched controls, whereas the response in patients with lower CD4 counts was not different from controls. At comparable concentrations, GM-CSF induced a significantly higher priming than G-CSF and IFN-g. A significant positive correlation between CD4 counts and priming activity of GM-CSF and IFN-g on neutrophils was observed. We conclude that neutrophils in HIV infection have a normal or enhanced response to the oxidative metabolism priming activity of hematopoietic growth factors in vitro, whereas priming effect on monocytes was not seen.
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PMID:Priming of neutrophil and monocyte activation in human immunodeficiency virus infection. Comparison of granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor and interferon-gamma. 897 88

The structural basis for the difference between human and murine CD4 molecules in binding to HIV envelope protein gp120 has been intensively studied. Eighteen mutant human CD4 molecules were produced by segmental replacement of beta strands and loops in the gp120-binding area of the molecule with corresponding murine sequences or by single amino acid substitutions. Examination of these mutant CD4 molecules for gp120 binding indicated that murine CD4 molecule does not bind gp120 for the following three reasons: (a) The loops flanking the C" strand are longer than their human counterparts, causing significant difference in local tertiary structure; (b) valin, rather than phenylalanine, which is the key amino acid for the binding occupies position 43; (c) amino acids at positions 45 and 46 are different, causing further decrease in binding affinity. Furthermore, the present study indicated that the aromatic ring of Phe43 and the negative charge of Arg59 play key roles in gp120 binding.
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PMID:Comparative analysis of the gp120-binding area of murine and human CD4 molecules. 898 4

Zidovudine (ZDV) is by far the most widely used drug to counteract human immunodeficiency virus type 1 (HIV-1) infection, both in monotherapy and in combination therapy regimens. However, the majority of patients under prolonged ZDV therapy have been shown to harbour HIV-1 mutant genomes displaying reduced sensitivity to the drug in vitro. In order to investigate the pathogenic role of in vitro resistance to ZDV, six HIV-1-infected ZDV-treated subjects were evaluated longitudinally (mean follow-up 28.5 months, range 12-39 months) for HIV-1 DNA load in peripheral blood mononuclear cells (PBMC) and for the presence of HIV-1 pol gene mutations responsible for ZDV resistance. Quantitation of HIV-1 DNA was performed by competitive polymerase chain reaction (cPCR) and the pol genotype was determined by direct sequencing of PCR products. All of the six patients developed one or more of the HIV-1 pol mutations known to confer resistance to ZDV in vitro (Met41-->Leu, Asp67-->Asn, Lys70-->Arg, Thr215-->Phe/Tyr, Lys219-->Gln/Glu). A temporal association was found between HIV-1 DNA burden and the level of ZDV resistance, as predicted on the basis of the pol genotype (genotypic resistance). Both virus load and ZDV resistance were inversely correlated with CD4+ cell counts. These results are compatible with a direct in vivo pathogenetic role for pol gene mutations shown to be involved in resistance to ZDV in vitro. Monitoring the degree of genotypic resistance to ZDV and to other antiretroviral drugs should be considered in designing protocols for the management of treated patients.
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PMID:Zidovudine resistance mutations and human immunodeficiency virus type 1 DNA burden: longitudinal evaluation of six patients under treatment. 900 88

The hydroxyethylurea human immunodeficiency virus type 1 (HIV-1) protease inhibitors SC-55389A and SC-52151 were used to select drug-resistant variants in vitro. One clinical HIV-1 strain (89-959) and one laboratory HIV-1 strain (LAI) were passaged in peripheral blood mononuclear cells or CEMT4 cells in the presence of SC-55389A. Resistant isolates from both strains consistently had a mutation to serine for asparagine at amino acid 88 (N88S) in the protease gene either alone or in combination with a change to phenylalanine at position 10. The N88S mutation, recreated by oligonucleotide-mediated site-directed mutagenesis in HXB2, was sufficient to confer resistance to SC-55389A. In contrast, SC-52151-resistant variants selected from the monocytotropic strain SF162 had multiple substitutions in the protease gene (I11V, M461, F53L, A71V, and N88D), and the N88D mutation, re-created by oligonucleotide-mediated site-directed mutagenesis in HXB2, did not confer resistance to SC-52151. The potencies of L735,524 and Ro31-8959 were not reduced when these compounds were assayed against variants with either the N88S or N88D substitution. Position 88 is in a helix that lies behind the substrate binding pocket and may indirectly influence inhibitor binding through interactions with the amino acid at position 31. The selected mutations were persistent in the viral populations after more than 20 passages in the absence of drugs. Passaging of virus first in SC-55389A alone and then in combination with SC-52151 resulted in the accumulation of more mutations in the protease gene (L10F, D35E, D37M, I47V, 154L, A71V, V82I, and S88D) and in the selection of a variant that was cross-resistant to multiple protease inhibitors. These results indicate that a mutation in the HIV-1 protease at a position that is located outside of the substrate binding pocket confers resistance to a protease inhibitor and that mutations in the protease gene accumulate with increasing selection pressure and can persist in the absence of selection pressure.
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PMID:A mutation in human immunodeficiency virus type 1 protease at position 88, located outside the active site, confers resistance to the hydroxyethylurea inhibitor SC-55389A. 905 85

Two different crystal structures of the human immunodeficiency virus type 1 (HIV-1) integrase (IN) catalytic domain were analyzed for interactions at the enzyme active site. Gln-62 and Glu-92 interact with active-site residue Asp-64, and Lys-136 interacts with active-site residue Asp-116 across a dimer interface. Conservative and nonconservative substitutions were introduced at these positions to probe the roles of these interactions in HIV-1 integration. Purified mutant proteins were assayed for in vitro 3' processing, DNA strand transfer, and disintegration activities, and HIV-1 mutants were assayed for virion protein composition, reverse transcription, and infectivities in human cell lines. Each of the mutant IN proteins displayed wild-type disintegration activity, indicating that none of the interactions is essential for catalysis. Mutants carrying Gln or Ala for Glu-92 displayed wild-type activities, but substituting Lys for Glu-92 reduced in vitro 3' processing and DNA strand transfer activities 5- to 10-fold and yielded a replication-defective IN active-site mutant viral phenotype. Substituting Glu for Gln-62 reduced in vitro 3' processing and DNA strand transfer activities 5- to 10-fold without grossly affecting viral replication kinetics, suggesting that HIV-1 can replicate in T-cell lines with less than the wild-type level of IN activity. The relationship between IN solubility and HIV-1 replication was also investigated. We previously showed that substituting Lys for Phe-185 dramatically increased the solubility of recombinant IN but caused an HIV-1 particle assembly defect. Mutants carrying His at this position displayed increased solubility and wild-type replication kinetics, showing that increased IN solubility per se is not detrimental to virus growth.
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PMID:Structure-based mutagenesis of the catalytic domain of human immunodeficiency virus type 1 integrase. 909 22

The retroviral proteases (PRs) have a structural feature called the flap, which consists of a short anti-parallel beta-sheet with a turn. The flap extends over the substrate binding cleft and must be flexible to allow entry and exit of the polypeptide substrates and products. We analyzed the sequence requirements of the amino acids within the flap region (positions 46-56) of the HIV-1 PR. The phenotypes of 131 substitution mutants were determined using a bacterial expression system. Four of the mutant PRs with mutations in different regions of the flap were selected for kinetic analysis. Our phenotypic analysis, considered in the context of published structures of the HIV-1 PR with a bound substrate analogs, shows that: (i) Met-46 and Phe-53 participate in hydrophobic interactions on the solvent-exposed face of the flap; (ii) Ile-47, Ile-54, and Val-56 participate in hydrophobic interactions on the inner face of the flap; (iii) Ile-50 has hydrophobic interactions at the distance of both the delta and gamma carbons; (iv) the three glycine residues in the beta-turn of the flap are virtually intolerant of substitutions. Among these mutant PRs, we have identified changes in both kcat and Km. These results establish the nature of the side chain requirements at each position in the flap and document a role for the flap in both substrate binding and catalysis.
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PMID:Sequence requirements of the HIV-1 protease flap region determined by saturation mutagenesis and kinetic analysis of flap mutants. 912 79

The peptide H-Asn-Ser-Trp-Gly-Cys-Ala-Phe-Arg-Gln-Val-Cys-NHEt corresponding to the 593-603 sequence of gp41 protein of the HIV-2 was used to evaluate different methods for the removal of Acm-protection and subsequent disulfide bond formation. The studied methods involved the treatment by salts of heavy metals (silver and mercury) and subsequent cyclization by oxygen, potassium ferricyanide or hydrogen peroxide. The direct oxidative conversion of Acm-peptide to the corresponding cyclic disulfide by iodine under acidic and neutral conditions was investigated, and the structure of by-products was also studied. The best results were obtained using mercuric acetate followed by oxidation with hydrogen peroxide.
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PMID:Comparative evaluation of different methods for disulfide bond formation in synthesis of the HIV-2 antigenic determinant. 912

The catELISA technique was modified and standardized for measuring HIV-1 aspartyl protease activity and evaluating the potency of synthetic peptide inhibitors. This immuno-quantified solid phase assay combines the use of an immobilized C-terminal biotinylated peptide as substrate, a crude enzyme preparation, and a highly specific antiserum elicited against the C-terminal product of the enzyme reaction. A standard curve of this C-terminal product was constructed to determine the enzyme activity. This assay, which requires less enzyme and substrate, is more sensitive than the conventional HPLC method. The amounts of C-terminal peptide produced in solution as determined from ELISA and HPLC standard curves were comparable. Analogues of peptidomimetics designed in our laboratory were assayed for their potency to inhibit the enzyme. One of them, H4, which is a hydroxyethylamine isostere of the Phe-Pro peptide bond, was a powerful inhibitor.
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PMID:Development and standardization of an immuno-quantified solid phase assay for HIV-1 aspartyl protease activity and its application to the evaluation of inhibitors. 914 28

The peptide sequence Gly-Pro-Gly-Arg-Ala-Phe (GPGRAF) is present in many principal neutralizing determinants (PND) of the human immunodeficiency virus type-1 (HIV-1). It has been shown that peptides from the PND sequence contain a significant beta turn in the conserved Gly-Pro-Gly-Arg sequence. In order to find out whether or not the smaller subunits also contain this turn, we have studied the NMR of a hexapeptide [GPGPRAF, peptide (I)], a heptapeptide Gly-Pro-Gly-Arg-Ala-Phe-Cys [GPGRAFC, peptide (II)] and a dodecapeptide [GPGRAFGPGRAF, peptide (III)], retaining the side chain protecting groups. Although the majority of conformations for these peptides are disordered, there is a considerable propensity of structures with beta turn in the GPGR sequence. While peptide (I) and peptide (III) seem to have both type I and type II beta turn conformations, peptide (II) shows a propensity of only type II beta turn. The nascent structures obtained in these peptides may get stabilized as the receptor binding conformation in the presence of the receptors, thus playing a significant role in vaccine development against HIV.
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PMID:NMR study of the peptide present in the principal neutralizing determinant (PND) of HIV-1 envelope glycoprotein gp120. 917 85


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