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: UMLS:C0021051 (immunodeficiency)
71,517 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two constituent protein domains of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase were expressed separately and purified to homogeneity. The N-terminal domain (p51) behaves as a monomeric protein exhibiting salt-sensitive DNA polymerase activity. The C-terminal domain (p15) on its own has no detectable RNase H activity. However, the combination of both isolated p51 and p15 in vitro leads to reconstitution of RNase H activity on a defined substrate. These results demonstrate that domains of HIV-1 reverse transcriptase are functionally interdependent to a much higher degree than in the case of reverse transcriptase from Moloney murine leukemia virus.
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PMID:Reconstitution in vitro of RNase H activity by using purified N-terminal and C-terminal domains of human immunodeficiency virus type 1 reverse transcriptase. 170 27

Mutations were introduced by recombinant DNA techniques into 9 genes of an infectious molecular clone of human immunodeficiency virus type 1. The 24 mutants generated were characterized biochemically and biologically by transfection and infection experiments. None of the mutants which have mutations in gag (p17, p24, and p15 regions), pol (protease, reverse transcriptase, and endonuclease domains), env (gp120 region), tat, or rev were infectious, whereas vif, vpr, vpu, some of env (gp41) and nef mutants could grow in human CD4+ cells to various degrees. Of the non-infectious mutants, only endonuclease (pol) and gp41 mutants exhibited normal phenotypes with respect to the production of functional reverse transcriptase, the expression of gag, pol, and env proteins, and the generation of progeny virions, when examined in transient assays. All infectious mutants killed the CD4+ cells with the exception of a mutant carrying a defect in the vif gene.
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PMID:Generation and characterization of the human immunodeficiency virus type 1 mutants. 170 90

The reverse transcriptase of human immunodeficiency virus type 1 is a heterodimeric protein consisting of two polypeptides with masses of 66 and 51 kDa and has, as a second enzymatic activity, RNase H activity. The 66-kDa polypeptide can be cleaved by the virus-encoded protease to yield polypeptides of 51 and 15 kDa. The latter has been characterized as possessing RNase H activity [Hansen, J., Schultze, T., Mellert, W. & Moelling, K. (1988) EMBO J. 7, 239-243]. We have purified simultaneously the heterodimeric reverse transcriptase/RNase H containing the 66/51-kDa polypeptides and the 15-kDa RNase H from Escherichia coli containing the expression vector pJS 3.7 by a procedure including chromatography on DEAE-cellulose, phosphocellulose, and heparin-Sepharose. Two RNase H and reverse transcriptase peaks were separated on phosphocellulose, one coinciding with the heterodimeric protein and the other with the 15-kDa protein. On the basis of the following findings it appears that the 15-kDa polypeptide has both RNase H and reverse transcriptase activities: (i) it copurified with both activities; (ii) it functioned as a reverse transcriptase in an in situ assay after SDS/polyacrylamide gel electrophoresis; (iii) polyclonal antibodies raised against the 66-kDa polypeptide reacted in immunoblots exclusively with a 15-kDa polypeptide, reacted in immunoblots exclusively with a 15-kDa polypeptide, while no immunoreactive bands in the range of 51-66 kDa were seen in the 15-kDa polypeptide preparation; (iv) the p15 and the p66/51 reverse transcriptase could be quantitatively pelleted in an enzymatically active form only when antibodies specific for the p66 carboxyl terminus were used; and (v) the p15 protein had bona fide properties of a reverse transcriptase and could enzymatically synthesize a high molecular weight, alkali-resistant product. The two reverse transcriptases appear to have different behaviors on various template/primer systems tested. Conceivably different forms of human immunodeficiency virus type 1 reverse transcriptases might be used in individual steps of (+)- and (-)-strand replication.
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PMID:The p15 carboxyl-terminal proteolysis product of the human immunodeficiency virus type 1 reverse transcriptase p66 has DNA polymerase activity. 171 Dec 22

The virally encoded protease of human immunodeficiency virus (HIV) is responsible for specific cleavage events leading to the liberation of the enzymes reverse transcriptase, integrase, ribonuclease H, and the core proteins from the gag-pol and gag polyprotein precursors. Utilizing gag polyprotein synthesized in vitro, we have shown that this substrate is sequentially cleaved by purified HIV protease to yield products that on the basis of their sizes and immunoreactivities correspond to p15, p6, p7, p17, and finally mature p24. We have placed unique restriction sites flanking the p17-p24 domain in order to facilitate replacement of cleavage site sequences by utilizing oligonucleotide cassettes. Replacement of the rapidly cleaved methionine-methionine bond at the p24-p15 junction with tyrosine-proline or replacement of the tyrosine-proline bond at the p17-p24 junction with methionine-methionine results in sites that cannot be efficiently cleaved. A basic amino acid at the p17-p24 scissile bond is not tolerated. Replacement of this cleavage site with an inverted repeat amino acid sequence gives intermediate rates of cleavage. In an attempt to convert the p17-p24 domain into a p24-p15 domain, residues flanking the scissile bond were exchanged in an expanding iterative fashion. When four residues flanking the scissile bond had been replaced, the rate of cleavage relative to that of the native p17-p24 sequence was increased fourfold. The cleavage rate of the native p24-p15 sequence is still some 10-fold greater than that of the p17-p24 sequence, suggesting that more-distant residues significantly affect the cleavage rate.
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PMID:Mutagenesis of protease cleavage sites in the human immunodeficiency virus type 1 gag polyprotein. 198 79

Cytoplasmic extracts prepared from cells infected with metabolically radiolabeled virions of human immunodeficiency virus type 1 contain viral DNA in association with labeled viral proteins. Viral DNA can be purified from these extracts by gel filtration chromatography and sucrose gradient sedimentation as a part of a nucleoprotein complex containing integrase as the only viral protein detectable by immunoprecipitation and gel electrophoretic analysis. The purified complex contains no detectable gag gene products, including p17, p24, p7, or p6, and contains no additional pol gene products, including the p10 protease, p66 and p51 polymerase, or the p15 RNase H. Nearly all of the purified nucleoprotein complexes are capable of integrating into heterologous DNA targets in vitro. These observations demonstrate that integrase is a component of the human immunodeficiency virus type 1 preintegration complex and suggest that integrase may be the only viral protein necessary for the integration of retroviral DNA.
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PMID:Determination of viral proteins present in the human immunodeficiency virus type 1 preintegration complex. 200 49

The nucleocapsid (NC) protein (p15) of the human immunodeficiency virus (HIV) has been cloned and overproduced (under the control of a phage T7 promoter) in soluble form in an Escherichia coli host. The soluble NC protein is a fusion protein containing 15 amino acids from the T7 gene 10 and 7 amino acids from the HIV p24 protein at the N-terminus to make a protein of 171 amino acids. The plasmid containing the fusion gene is designated p15DF. A homogeneous product has been isolated from the induced cells and, when isolated under aerobic conditions, contains 0.3-0.5 mol of Zn/mol of protein and has only 2 titratable SH groups. Reduction and refolding in the presence of Zn(II) yields a protein containing 2.0 mol of Zn/mol of protein and 6 titratable SH groups. On the other hand, if the cells are sonicated in 2 mM CdCl2 and purified at pH 5.0, an unoxidized protein containing 2 mol of Cd/mol of protein is obtained. The Cd(II) ions can be exchanged with Zn(II), Co(II), or 113Cd(II). The Co(II)2 NC protein shows d-d electronic transitions at 695 nm [epsilon = 675 M-1 cm-1 per Co(II)] and 640 nm [epsilon = 825 M-1 cm-1 per Co(II)] compatible with regular tetrahedral geometry around both Co(II) ions. The Co(II)2 and Cd(II)2 NC proteins show intense charge-transfer bands in the near-UV, at 355 nm (epsilon = approximately 4000 M-1 cm-1) and 310 nm (epsilon = approximately 8000 M-1 cm-1) for the Co(II) protein and 255 nm (epsilon = approximately 10(4) M-1 cm-1) for the Cd(II)2 NC protein, compatible with -S- coordination. 113Cd NMR of the 113Cd(II)2 NC protein shows two 113Cd NMR signals at 659 and 640 ppm, respectively, each integrating to approximately 1 Cd(II) ion. The downfield chemical shifts suggest coordination of each 113Cd(II) ion to 3 sulfur donor atoms. The spectroscopic data fully support the prediction that the NC protein binds metal ions to each of the tandem repeats of the -Cys-X2-Cys-X4-His-X4-Cys- sequence contained in the N-terminal half of the molecule. 113Cd NMR shows, however, that the sites are not identical. Isolation of the NC protein under standard aerobic conditions results in oxidation of the sulfhydryl groups and loss of the coordinated Zn(II) ions, while preparation of the NC protein as the Cd(II) derivative at low pH protects the sulfhydryl groups from oxidation.
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PMID:Physicochemical properties of cloned nucleocapsid protein from HIV. Interactions with metal ions. 203 85

Novel fluorogenic substrates for human immunodeficiency viral protease have been developed based on the principle of fluorescence energy transfer. Starting from a p24/p15 cleavage site-derived hexapeptide substrate. Ac-Thr-Ile-Nle-Nle-Gln-Arg-NH2, incorporation of 2-aminobenzoic acid in place of the acetyl group as the donor and p-NO2-Phe at the P1' position as acceptor gave the intramolecularly quenched fluorogenic substrate. Cleavage of the substrate by HIV protease released the fluorescent N-terminal tripeptide from its close apposition to the quenching nitrobenzyl group, resulting in enhanced fluorescence. An automated assay based on 96-well microtiter plates and a fluorometric plate reader have been developed, which allow high throughput of compounds in the search for HIV protease inhibitors.
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PMID:A simple, continuous fluorometric assay for HIV protease. 209 Jun 47

Follicular dendritic cells (FDC) from axillary lymphoid tissue of a patient with acquired immune deficiency syndrome (AIDS) were analyzed for the presence of gag and env proteins and env mRNA of human immunodeficiency virus type-1 (HIV-1), both in a purified FDC suspension and on frozen sections. Isolated cells with morphologic and immunocytochemical features of FDC expressed HIV-1 core (gag) proteins p15, p17, p24, and envelope (env) protein gp41; in addition HIV-1 env mRNA was detected in some of these cells. This corresponded with intense expression of HIV-1 proteins by FDC in germinal centers in situ, and the presence of HIV-1 mRNA-positive cells in germinal follicles. These findings led us to conclude that FDC are infected and able to produce HIV-1. Such infection may contribute significantly to the destruction of the FDC network during the lymphadenopathy phase after HIV-1 infection.
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PMID:HIV-1 infection and virus production in follicular dendritic cells in lymph nodes. A case report, with analysis of isolated follicular dendritic cells. 211 96

Recombinant vaccinia viruses that contained regions of the gag-pol open reading frames of human immunodeficiency virus type 1 (HIV-1) were constructed. Cells infected with recombinants containing both gag and protease genes expressed and processed HIV gag antigens efficiently. Processing was much reduced in cells infected with recombinants containing only gag, but not the protease gene. However, significant amounts of p41 were produced by protease-defective recombinants. This protein was immunoreactive with p24-specific monoclonal antibodies and was produced in a truncated form by a recombinant containing a 3' deletion in the p15 coding region of gag ORF. These results indicate that p41 could represent an alternative gag precursor with N-terminal sequences derived from p24 and C-terminal from p15. Ultrastructural analysis of recombinant-infected cells revealed that the gag antigens expressed were assembled into retrovirus-like particles and were secreted into culture medium. This assembly process was not dependent on HIV protease function, because immature core particles were produced by recombinants lacking HIV-1 protease functions. Immunization of mice and chimpanzees with vaccinia-HIVgag recombinant viruses generated both antibody and cell-mediated immune responses to HIV gag antigens. These recombinants are therefore useful not only for studying HIV virion processing and assembly, but also for designing immunogens for the prophylaxis and immunotherapy against AIDS.
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PMID:Processing, assembly, and immunogenicity of human immunodeficiency virus core antigens expressed by recombinant vaccinia virus. 221 27

A segment of the gag gene of the human immunodeficiency virus (HIV) (HTLV-IIIB strain), the virus which causes acquired immunodeficiency syndrome (AIDS), has been cloned into the bacterial expression vector, pCQV2, and mapped to the right-hand portion of the gag gene containing the carboxyl-terminal portion of p24 and the amino-terminal portion of p15. Nucleic-acid sequencing of the insert-vector junctions further defined the 5'-terminal nucleotide of HIV sequence as nucleotide 997 and the 3'-terminal nucleotide as 1696. When used in an enzyme-linked immunosorbent assay (ELISA) with sera from HIV-infected patients, the cloned antigen reacted with a subset of sera which were positive on a standard ELISA using whole virus as antigen. Western-blot screening of these sera with whole virus indicated that all p24-positive sera were positive with the clone, suggesting that the carboxyl-terminal portion of p24 contains a highly antigenic epitope(s). A serum which was p24-negative p15-positive by Western blot analysis was also highly reactive, indicating that a p15 epitope is present in the cloned antigen. Epitope mapping with a series of monoclonal antibodies to gag resulted in positive ELISA with 2 of 3 anti-p24, 0 of 1 anti-p15, and 0 of 1 anti-p17 Western-blot-positive monoclonal antibodies, suggesting that one of the anti-p24 monoclonal antibodies reacts with epitopes amino-terminal to those coded from nucleotide 997, two anti-p24 monoclonals react with epitopes carboxyl-terminal to those coded from nucleotide 997, and the anti-p15 monoclonal reacts with epitopes carboxyl-terminal to those coded from nucleotide 1696.
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PMID:Reactivity of an HIV gag gene polypeptide expressed in E. coli with sera from AIDS patients and monoclonal antibodies to gag. 244 45


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