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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

All retroviral nucleocapsid (NC) proteins contain one or two copies of an invariant 3Cys-1His array (CCHC = C-X2-C-X4-H-X4-C; C = Cys, H = His, X = variable amino acid) that are essential for RNA genome packaging and infectivity and have been proposed to function as zinc-binding domains. Although the arrays are capable of binding zinc in vitro, the physiological relevance of zinc coordination has not been firmly established. We have obtained zinc-edge extended X-ray absorption fine structure (EXAFS) spectra for intact retroviruses in order to determine if virus-bound zinc, which is present in quantities nearly stoichiometric with the CCHC arrays (Bess, J.W., Jr., Powell, P.J., Issaq, H.J., Schumack, L.J., Grimes, M.K., Henderson, L.E., & Arthur, L.O., 1992, J. Virol. 66, 840-847), exists in a unique coordination environment. The viral EXAFS spectra obtained are remarkably similar to the spectrum of a model CCHC zinc finger peptide with known 3Cys-1His zinc coordination structure. This finding, combined with other biochemical results, indicates that the majority of the viral zinc is coordinated to the NC CCHC arrays in mature retroviruses. Based on these findings, we have extended our NMR studies of the HIV-1 NC protein and have determined its three-dimensional solution-state structure. The CCHC arrays of HIV-1 NC exist as independently folded, noninteracting domains on a flexible polypeptide chain, with conservatively substituted aromatic residues forming hydrophobic patches on the zinc finger surfaces. These residues are essential for RNA genome recognition, and fluorescence measurements indicate that at least one residue (Trp37) participates directly in binding to nucleic acids in vitro. The NC is only the third HIV-1 protein to be structurally characterized, and the combined EXAFS, structural, and nucleic acid-binding results provide a basis for the rational design of new NC-targeted antiviral agents and vaccines for the control of AIDS.
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PMID:Nucleocapsid zinc fingers detected in retroviruses: EXAFS studies of intact viruses and the solution-state structure of the nucleocapsid protein from HIV-1. 130 55

The Zn2+ binding properties of the synthetic nucleocapsid protein (Ncp7) of HIV-1, containing two zinc-binding domains, have been studied using electrospray mass spectrometry (ES-MS). ES-MS measurements revealed strong binding of Zn2+ by Ncp7. Its shorter fragments, Ncp7-(1-35)- and (29-55)-peptides, each containing only one zinc-binding domain, bind one equivalent of Zn2+ ions tightly. ES-MS studies allows these fragments to be distinguished in terms of their binding affinity: they showed stronger binding of Zn2+ by Ncp7-(1-35)-peptide. Surprisingly, in addition to the expected two zinc-binding domains, a third metal binding site was detected in Ncp7. However, this site appears to bind different metal ions without selectivity and most probably reflects salt formation at the C-terminal acidic residues.
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PMID:Nucleocapsid protein of HIV-1 and its Zn2+ complex formation analysis with electrospray mass spectrometry. 139 25

A simple synthesis of the sulfonated azo dye Quinobene (3) and its derivatives, as well as the results of their evaluation in anti-HIV screening have been described. Thus, reacting the diazonium salt of 4,4'-diaminostilbene-2,2'-disulfonic acid with 8-hydroxyquinoline-5-sulfonic acid yielded the readily isolable title compound. The lithium and tetramethylammonium salts of Quinobene and its complexes with Cu(II), Zn(II), Mg(II) were also prepared. In vitro tests showed considerable activity of these compounds against HIV-1.
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PMID:Quinobene, a new potent anti-HIV agent. 141 17

Recombinant HIV-1 Tat (Tat 1-86) has been purified from the cytoplasmic fraction of Escherichia coli without the use of protein denaturants or chaotropic agents. Chloroquine-mediated uptake of the purified protein into cells resulted in transactivation of the HIV LTR promoter. Tat retains 1.64 mol of Zn2+/mol of protein by atomic absorption spectroscopy. Circular dichroism measurements indicated that the structure of recombinant Tat contains 15-20% alpha-helix. Filter binding assays showed that Tat binds to a 63-nucleotide target TAR RNA with a dissociation constant (Kd) of 10 nM at 25 degrees C, 0.05 M ionic strength, pH 7.5, in a 1:1 Tat-TAR RNA stoichiometry. Nonelectrostatic interactions provide the principal source of free energy of association. While the pH optimum occurs over a wide H+ concentration, the salt dependence of Kd indicates formation of a single ion pair. UV-induced protein-RNA cross-linking produced a labeled Tat-TAR RNA adduct, indicating that direct contact occurred between the Tat protein and TAR RNA.
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PMID:Characterization of recombinant HIV-1 Tat and its interaction with TAR RNA. 145 3

The nucleocapsid protein (NC) of all animal retroviruses, encoded by the gag gene, is the major structural protein of the core ribonucleoprotein complex, bound to genomic RNA in mature virions. NC is also thought to play one or more accessory roles in reverse transcription. Mature NC (p7NC) from human immunodeficiency virus type 1 (HIV-1) is a 71-amino acid, basic protein which contains two Cys3His Zn(II) retroviral-type zinc finger domains. Herein, we describe the subcloning and expression of HIV-1 NC, denoted NC71, from an inducible phage T7 RNA polymerase promoter in Escherichia coli. Purified NC71 can be reversibly reconstituted with 2 g.at Zn(II) determined by atomic absorption. Ultraviolet circulation dichroism spectroscopy has been used to characterize the complexes between highly purified NC71 and the RNA homopolynucleotide poly(A) and E. coli tRNA(mixed). On poly(A), Zn2 NC71 is characterized by an apparent site size n = 15 +/- 3 nucleotides and high affinity (Kapp = 3 x 10(7) M-1) and moderately cooperative (omega approximately 170 +/- 25) binding. A mixture of E. coli tRNA species (tRNA(mixed) was used to probe the conformational changes induced in tRNA upon binding of HIV-1 NC71. Two structural forms of tRNA(mixed), which differ in their degree of tertiary structure, were assayed for their susceptibility to denaturation by NC71. Five molar monomer equivalents of NC71 are required to denature the "inactive" tRNA in the absence of Mg2+. A Zn(II)-free, oxidized form of NC71 was also shown to unwind inactive tRNA with the same efficiency and stoichiometry. The detailed spectral changes which occur on NC-induced denaturation closely mimic temperature-induced denaturation of inactive tRNA(mixed). The prototype helix-destabilizing protein, T4 gene 32 protein, is unable to unwind this form of tRNA under the same conditions. The stoichiometry of unwinding of inactive tRNA by NC71 is consistent with the site size determined with poly(A). An "active" form of tRNA(mixed), prepared by thermal denaturation and refolding of the inactive form with Mg2+, proved less susceptible to both temperature and NC71-induced unwinding. The mechanistic implications of these findings on the reported biochemical activities of RNA:RNA annealing and replication primer tRNA positioning by NC are discussed.
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PMID:Recombinant human immunodeficiency virus type 1 nucleocapsid (NCp7) protein unwinds tRNA. 155 77

The N-terminal domain of human immunodeficiency virus (HIV-1) integrase (IN) contains the sequence motif His-Xaa3-His-Xaa23-Cys-Xaa2-Cys, which is strongly conserved in all retroviral and retrotransposon IN proteins. This structural motif constitutes a putative zinc finger in which a metal ion may be coordinately bound by the His and Cys residues. A recombinant peptide, IN(1-55), composed of the N-terminal 55 amino acids of HIV-1 IN was expressed in Escherichia coli and purified. Utilizing a combination of techniques including UV-visible absorption, circular dichroism, Fourier transform infrared, and fluorescence spectroscopies, we have demonstrated that metal ions (Zn2+, Co2+, and Cd2+) are bound with equimolar stoichiometry by IN(1-55). The liganded peptide assumes a highly ordered structure with increased alpha-helical content and exhibits remarkable thermal stability. UV-visible difference spectra of the peptide-Co2+ complexes directly implicate thiols in metal coordination, and Co2+ d-d transitions in the visible range indicate that Co2+ is tetrahedrally coordinated. Mutant peptides containing conservative substitutions of one of the conserved His or either of the Cys residues displayed no significant Zn(2+)-induced conformational changes as monitored by CD and fluorescence spectra. We conclude that the N terminus of HIV-1 IN contains a metal-binding domain whose structure is stabilized by tetrahedral coordination of metal by histidines 12 and 16 and cysteines 40 and 43. A preliminary structural model for this zinc finger is presented.
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PMID:Structural implications of spectroscopic characterization of a putative zinc finger peptide from HIV-1 integrase. 157 1

HIV-1 integrase binds to both double- and single-stranded DNA with Kd-values of around 20 nM, irrespective of sequence similarities with the termini of the viral LTR. For integration activity, however, the correct LTR sequence of the substrate is required. The putative zinc-binding site present at the N-terminus of the protein is not essential for DNA binding, since deletion mutants of the protein lacking this sequence show similar affinity towards DNA as the wild-type; however, these mutants are not capable of performing the LTR-cleavage and integration reactions. Thus, it appears that the N-terminal part of the integrase is essential for catalytic activity.
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PMID:The N-terminal region of HIV-1 integrase is required for integration activity, but not for DNA-binding. 162 42

Zinc is a mitogen for peripheral blood mononuclear cells (PBMC). The optimal mitogenic concentration was found to be 0.05 mmol/l (327 micrograms/dl), four times higher than physiological serum levels. Maximal proliferation was observed after 6 days. Limited dilution technique revealed a frequency of zinc reactive cells of 1:3467 (median; range 1:1628-1:6235). Cord blood mononuclear cells from four of six healthy children could be stimulated to proliferate by zinc. A normal zinc-induced proliferative response could be demonstrated in all six HIV-infected patients in the Walter-Reed-stage I, in nine of 11 patients in Walter-Reed II and in only two of five patients in Walter-Reed III. In Walter-Reed IV to VI all eight patients showed a weak response to zinc (less than 50% of the healthy day control). Decreased zinc serum levels were found in 10 of 28 patients and in one of 16 controls. There was a significant correlation of a diminished zinc-induced proliferation with lower serum levels of zinc and a reduced proportion of CD4 helper cells in HIV-1-infected men. Because of a suppression of mitogenesis by high dose of zinc an excessive intake of zinc as used by some HIV-1-infected patients can presently not be recommended. The value of zinc-induced proliferation for monitoring HIV-infected patients has still to be established.
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PMID:In vitro activation of peripheral mononuclear cells by zinc in HIV-infected patients and healthy controls. 163 72

The retroviral gag nucleocapsid protein NCp7 (72 amino acids) of HIV-1 (LAV strain), which contains two successive zinc fingers of the Cys-X2-Cys-X4-His-X4-Cys form linked by a stretch of basic residues, promotes viral RNA dimerization and encapsidation and activates annealing of the primer tRNA to the initiation site of reverse transcription. The structure of NCp7 and other shorter fragments was studied by 600 MHz 1H nuclear magnetic resonance (NMR) in aqueous solution to account for its various biological properties. Complete sequence specific 1H NMR assignments of the 13-51 residues of NCp7 encompassing the two zinc fingers was achieved by two-dimensional NMR experiments and the three-dimensional structure of (13-51)NCp7 was deduced from DIANA calculations, using nuclear Overhauser effects as constraints. The structure of the zinc complexed form of NCp7 is characterized by a kink at the Pro31 level in the basic Arg29-Ala-Pro-Arg-Lys-Lys-Gly35 RNA binding linker leading to a proximity of the Lys14-Cys18 to the Gly35-Cys39 sequences, which belong to the folded proximal and distal zinc fingers, respectively. Accordingly, the aromatic residues Phe16 and Trp37 were found to be spatially close. The Lys33 and Lys34 side-chains involved in viral RNA dimerization were solvent exposed. The N- and C-terminal sequences of NCp7 behave as flexible independent domains. The proposed structure of NCp7 might be used to rationally design new anti-viral agents aimed at inhibiting its functions.
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PMID:Determination of the structure of the nucleocapsid protein NCp7 from the human immunodeficiency virus type 1 by 1H NMR. 163 74

Large amounts of histones, H1, H2A, H2B, H3, and H4, were observed in total extracts of T4 lymphocytes and derived cell lines infected with the human immunodeficiency virus (HIV) type 1 or type 2. These histones were simply detectable by analysis of crude cellular extracts by polyacrylamide gel electrophoresis in SDS and staining the proteins with Coomassie blue or by immunoblot assays using specific polyclonal antibodies. The histones were found to be localized in the nucleoplasm, bound to low molecular weight (LMW) DNA in the form of nucleosomes. The mechanism responsible for the accumulation of nucleosomes during HIV infection was found to be due to fragmentation of cellular DNA, a mechanism referred to as apoptosis or programmed cell death in which a nuclear endonuclease becomes activated and cleaves DNA at internucleosomal regions. Accordingly, the LMW DNA accumulated in the course of infection was found to have a characteristic pattern of nucleosomal ladder and its accumulation was reduced in the presence of zinc, a known inhibitor of the endonuclease. Routinely in acute HIV infections, the accumulation of nucleosomes was observed at least 24 hr before lysis of infected cells. In a particular HIV-1 infection, in which the first signals of the cytopathic effect (vacuolization of cells and appearance of syncytia) was observed at Days 6-7 whereas maximal virus production occurred at Days 10-17, the accumulation of nucleosomes was at its maximal level already on Day 6 postinfection. In the nucleoplasm of chronically infected cells producing virus but not manifesting a cytopathic effect, no LMW DNA or histones were detectable. These observations indicate that the cytopathic effect of HIV infection is associated with apoptosis. The detection of histones and oligonucleosomal DNA fragments in the nucleoplasm can be used as a convenient marker for chromatin fragmentation during this process.
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PMID:The cytopathic effect of HIV is associated with apoptosis. 168 28


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