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)

Peptide T, from the human immunodeficiency virus (HIV), whose sequence is Ala-Ser-Thr-Thr-Thr-Asn-Tyr-Thr, has been shown to inhibit attachment of this virus to T cells and neural cells bearing the CD4 receptor. This peptide shares extensive homology with the 19-26 segment of ribonuclease A (RNase A), whose sequence is Ala-Ala-Ser-Ser-Ser-Asn-Tyr-Cys. Based on comparison of the structures of peptides occurring in proteins of known structure that are homologous to peptide T, viz, RNase A and endothiapepsin and on conformational energy calculations, we predicted that peptide T adopts a structure much like that for residues 19-26 in RNase A. A critical feature is a bend involving residues Thr 4-Asn 7 in peptide T corresponding to Ser 22-Tyr 25 in the RNase A peptide. Our proposed structure for peptide T has recently been confirmed by Cotelle et al. (Biochem. Biophys. Res. Commun. 171, 596-602). We now show directly that the RNase A peptide, with Met replacing Cys 26 to prevent disulfide exchange reactions, strongly induces monocyte-chemotaxis that is blocked by anti-CD4 monoclonal antibody. Both peptide T and RNase A fail to induce chemotaxis, however, in neutrophils which do not express surface CD4 receptors. These results suggest that both peptides interact with the CD4 receptor in inducing monocyte chemotaxis. We have also prepared cyclo-RNase A peptide with Met 26. Using molecular dynamics and conformational energy calculations, we find that the cyclic peptide cannot form a bend structure involving Ser 22-Tyr 25 that is superimposable on the RNase A bend.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Correlation of the conformation of a modified ribonuclease octapeptide, homologous to peptide T, with its ability to induce CD4-dependent monocyte chemotaxis. 144 97

The first immunoglobulin V-like domain of CD4 contains the binding site for human immunodeficiency virus gp120. Guided by the atomic structure of a two-domain CD4 fragment, we have examined gp120 interaction with informative CD4 mutants, both by equilibrium and kinetic analysis. The binding site on CD4 appears to be a surface region of about 900 A2 on the C" edge of the domain. It contains an exposed hydrophobic residue, Phe43, on the C" strand and four positively charged residues, Lys29, Lys35, Lys46, and Arg59, on the C, C', C", and D strands, respectively. Replacement of Phe43 with Ala or Ile reduces affinity for gp120 by more than 500-fold; Tyr, Trp, and Leu substitutions have smaller effects. The four positively charged side chains each make significant contributions (7-50-fold). This CD4 site may dock into a conserved hydrophobic pocket bordered by several negatively charged residues in gp120. Class II major histocompatibility complex binding includes the same region on CD4; this overlap needs to be considered in the design of inhibitors of the CD4-gp120 interaction.
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PMID:The human immunodeficiency virus gp120 binding site on CD4: delineation by quantitative equilibrium and kinetic binding studies of mutants in conjunction with a high-resolution CD4 atomic structure. 150 Aug 58

Protein tyrosine phosphorylation is a common mechanism of signaling in pathways that regulate T cell receptor-mediated cell activation, cell proliferation, and the cell cycle. Because human immunodeficiency virus (HIV) is though to affect normal cell signaling, tyrosine phosphorylation may be associated with HIV cytopathicity. In both HIV-infected cells and transfected cells that stably express HIV envelope glycoproteins undergoing HIVgp41-induced cell fusion, a 30-kilodalton protein was phosphorylated on tyrosine with kinetics similar to those of syncytium formation and cell death. When tyrosine phosphorylation was inhibited by the protein tyrosine kinase inhibitor herbimycin A, envelope-mediated syncytium formation was coordinately reduced. These studies show that specific intracellular signals, which apparently participate in cytopathicity, are generated by HIV and suggest strategies by which the fusion process might be interrupted.
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PMID:Participation of tyrosine phosphorylation in the cytopathic effect of human immunodeficiency virus-1. 157 May 14

A critical step in the replicative cycle of the human immunodeficiency virus HIV-1 involves the proteolytic processing of the polyprotein products Prgag and Prgag-pol that are encoded by the gag and pol genes in the viral genome. Inhibitors of this processing step have the potential to be important therapeutic agents in the management of acquired immunodeficiency syndrome. Current assays for inhibitors of HIV-1 protease are slow, cumbersome, or susceptible to interference by test compounds. An approach to the generation of a rapid, sensitive assay for HIV-1 protease inhibitors that is devoid of interference problems is to use a capture system which allows for isolation of the products from the reaction mixture prior to signal quantitation. In this paper, we describe a novel method for the detection of HIV-1 protease inhibitors utilizing the concept of particle concentration fluorescence. Our approach involves the use of the HIV-1 protease peptide substrate Ser-Gln-Asn-Tyr-Pro-Ile-Val which has been modified to contain a biotin moiety on one side and a fluorescein reporter molecule on the other side of the scissile Tyr-Pro bond. This substrate is efficiently cleaved by the HIV-1 protease and the reaction can be readily quantitated. Known inhibitors of the protease were readily detected using this new assay. In addition, this approach is compatible with existing instrumentation in use for broad screening and is highly sensitive, accurate, and reproducible.
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PMID:Design and implementation of a particle concentration fluorescence method for the detection of HIV-1 protease inhibitors. 162 70

The T lymphocyte surface protein CD4 is an integral membrane glycoprotein noncovalently associated with the tyrosine protein kinase p56lck. In normal T cells, surface association of CD4 molecules with other CD4 molecules or other T-cell surface proteins, such as the T-cell antigen receptor, stimulates the activity of the p56lck tyrosine kinase, resulting in the phosphorylation of various cellular proteins at tyrosine residues. Thus, the signal transduction in T cells generated through the surface engagement of CD4 is similar to that observed for the class of growth factor receptors possessing endogenous tyrosine kinase activity. As CD4 is also the cellular receptor for the human immunodeficiency virus (HIV), binding of the virus or gp120 (the virus surface protein responsible for specific CD4+ T-cell association) could mimic the types of immunological interactions that have previously been found to stimulate p56lck and trigger T-cell activation pathways. We have evaluated this possibility and report here that binding of HIV-1 or the virus glycoprotein gp120 to CD4+ human T cells fails to elicit detectable p56lck-dependent tyrosine kinase activation and signalling, alterations in the composition of cellular phosphotyrosine-containing proteins, or changes in intracellular Ca2+ concentration.
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PMID:No T-cell tyrosine protein kinase signalling or calcium mobilization after CD4 association with HIV-1 or HIV-1 gp120. 170 Oct 34

Bleomycin is an antitumor agent whose activity has long been thought to derive from its ability to degrade DNA. Recent findings suggest that cellular RNA may be a therapeutically relevant locus. At micromolar concentrations, Fe(II)-bleomycin readily cleaved a Bacillus subtilis tRNAHis precursor in a highly selective fashion, but Escherichia coli tRNA(Tyr) precursor was largely unaffected even under more forcing conditions. Other substrates included an RNA transcript encoding a large segment of the reverse transcriptase from human immunodeficiency virus 1. RNA cleavage was oxidative, approximately 10-fold more selective than DNA cleavage, and largely unaffected by nonsubstrate RNAs. RNA sequence analysis suggested recognition of RNA tertiary structure, rather than recognition of specific sequences; subsets of nucleotides at the junction of single- and double-stranded regions were especially susceptible to cleavage. The ready accessibility of cellular RNAs to xenobiotic agents, the high selectivity of bleomycin action on RNAs, and the paucity of mechanisms for RNA repair suggest that RNA may be a therapeutically relevant target for bleomycin.
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PMID:Site-specific cleavage of RNA by Fe(II).bleomycin. 170 Dec 59

A quantitative rapid assay to detect resistant clinical human immunodeficiency virus type 1 (HIV-1) strains remains an important medical goal. A system incorporating a quantitative RNA.RNA hybridization assay that measures the amount of intracellular HIV-1-specific RNA has been employed to detect the level of inhibition by nucleoside analogues in sensitive and resistant HIV-1 strains. The RNA.RNA hybridization assay readily distinguished previously published zidovudine (ZDV; 3'-azido-3'-deoxythymidine)-resistant isolates from ZDV-sensitive isolates of HIV-1. The 50% inhibitory concentration (IC50) of ZDV for HTLV-IIIB and sensitive clinical HIV-1 isolates is between 0.01 and 0.04 microM. HIV-1 strains from three patients on long-term ZDV therapy displayed a greater than 20-fold increase in the ZDV IC50 compared to sensitive strains. The drug sensitivity system was confirmed by showing that mutations in the HIV reverse transcriptase gene from a ZDV-resistant isolate resulted in four amino acid changes (Leu-125----Trp, Ile-142----Val, Thr-215----Tyr, and Pro-294----Thr) including one change (Thr-215----Tyr) that has been previously reported to be associated with resistance. One clinical HIV strain with high-level ZDV resistance displayed a 5-fold increase in 2',3'-dideoxyinosine IC50 compared to that of HTLV-IIIB. A drug sensitivity assay employing RNA.RNA hybridization may be useful for extensive screening of HIV isolates from patients enrolled in clinical trials and permit the correlation of in vitro resistance with clinical outcome.
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PMID:Detection of human immunodeficiency virus type 1 clinical isolates with reduced sensitivity to zidovudine and dideoxyinosine by RNA.RNA hybridization. 170 32

Nevirapine (BI-RG-587) is a potent and specific non-nucleoside inhibitor of human immunodeficiency virus type-1 reverse transcriptase. The compound is non-competitive with respect to template, primer, and nucleoside triphosphates indicating that BI-RG-587 does not act directly at the catalytic site. The binding site for this inhibitor was investigated by employing an azido photoaffinity analogue, BI-RJ-70, to covalently label the enzyme. The resulting photoadduct was subjected to enzymatic digestion by trypsin and endoproteinase lys-C and a single, highly labeled peptide was identified as residues 174-199. Sequencing of this peptide identified Tyr-181 and Tyr-188 as labeled residues.
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PMID:Characterization of the binding site for nevirapine (BI-RG-587), a nonnucleoside inhibitor of human immunodeficiency virus type-1 reverse transcriptase. 171 87

An anti-human immunodeficiency virus (anti-HIV) protein capable of inhibiting HIV-1 infection and replication has been isolated and purified to homogeneity from Trichosanthes kirilowii. This protein, TAP 29 (Trichosanthes anti-HIV protein, 29 kDa), is distinct from trichosanthin [also known as GLQ 223 (26 kDa)] in size, N-terminal amino acid sequence, and cytotoxicity. In addition to three conservative substitutions--namely, Arg-29 to Lys, Ile-37 to Val, and Pro-42 to Ser--a total difference of residues 12-16 was found. TAP 29 yielded -Lys-Lys-Lys-Val-Tyr-, whereas trichosanthin has -Ser-Ser-Tyr-Gly-Val-. Although the two proteins exhibit similar anti-HIV activity, as measured by syncytium formation, p24 expression, and HIV reverse transcriptase activity, they differ significantly in cytotoxicity, as measured by their effects on cellular DNA and protein syntheses. At the dose level of the bioassays, 0.34-340 nM, trichosanthin demonstrates a dose-dependent toxic effect on host cells. TAP 29 displays no toxic effect, even at 100 X ID50, whereas trichosanthin demonstrates 38% and 44% inhibition on cellular DNA and protein synthesis, respectively. These results indicate that the therapeutic index of TAP 29 is at least two orders of magnitude higher than that of trichosanthin. Thus TAP 29 may offer a broader safe dose range in the treatment of AIDS.
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PMID:TAP 29: an anti-human immunodeficiency virus protein from Trichosanthes kirilowii that is nontoxic to intact cells. 171 84

We have recently described a nonnucleoside compound that specifically inhibits the reverse transcriptase of human immunodeficiency virus type 1 (HIV-1), the causative agent of AIDS. This compound, nevirapine (BI-RG-587), interacts with highly conserved tyrosine residues at positions 181 and 188 in the reverse transcriptase to inhibit the recombinant enzyme and virus replication in cell culture with 50% inhibitory concentrations in the 40 nM range. HIV-1 variants resistant to nevirapine emerged with passage in cell culture in the presence of drug. This resistant phenotype was stable with continued passage in the absence of drug. These mutants had a substitution of cysteine for the tyrosine at position 181. Introduction of this mutation into the recombinant enzyme increased the inhibitory concentration of nevirapine 100-fold. Substitution of cysteine for tyrosine at residue 181 into the wild-type viral genome conferred a similar reduction in susceptibility to nevirapine. Mutants were also resistant to a tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-one and -thione derivative and two 6-phenylthiouracil derivatives but retained their sensitivity to the other reverse transcriptase inhibitors, 3'-azido-3'-deoxythymidine and foscarnet.
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PMID:Human immunodeficiency virus type 1 mutants resistant to nonnucleoside inhibitors of reverse transcriptase arise in tissue culture. 172 24


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