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)

The redox chemistry of two synthetic model peptides for the 603-609 disulfide loop found in envelope glycoprotein gp41 of the human immunodeficiency virus type 1 (HIV-1) are reported. The two peptides: N-Ac-Trp-Gly-Cys-Ser-Gly-Lys-Leu-Ile-Cys-Thr-Thr-NH2 (I) and N-Ac-Trp-Gly-Cys-Ser-Gly-Arg-His-Ile-Cys-Thr-Thr-NH2 (II) were synthesized by the solid phase method. Peptide I corresponds to amino acids 601-611 of gp41 of the North American/European strain of HIV-1. Peptide II incorporates amino acid replacements frequent in African HIV-1 isolates. The redox chemistry of the disulfide bonds in the two peptides was characterized in aqueous and aqueous/urea solution by studying their thiol-disulfide exchange reactions with the tripeptide glutathione (GSH). GSH reacts with the disulfide bonds to form mixed disulfides, which in turn react with another molecule of GSH to give the dithiol form of the peptide and GSSG. Equilibrium constants were determined for each step and for the overall reduction reactions. Redox potentials of -0.246V and -0.241V were calculated from the equilibrium constants for the disulfide bonds in peptides I and II in aqueous solution at 25 degrees C and pH 7.0. The overall equilibrium constants are less in 8 M urea solution, which indicates a stabilization of the reduced, dithiol form of both peptides by secondary structure which can be denatured by urea. This conclusion is supported by nuclear Overhauser enhancement data obtained from 2D-ROESY NMR spectra which provide evidence of elements of secondary structure for the reduced forms of both peptides. The results are discussed in terms of a protein disulfide isomerase catalyzed reduction of the disulfide bond in gp41.
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PMID:Characterization of the thiol/disulfide chemistry of peptides corresponding to the 603-609 disulfide loop of the human immunodeficiency virus (HIV) envelope glycoprotein gp41. 965 Jul 18

The solution structure of the ectodomain of simian immunodeficiency virus (SIV) gp41 (e-gp41), consisting of residues 27-149, has been determined by multidimensional heteronuclear NMR spectroscopy. SIV e-gp41 is a symmetric 44 kDa trimer with each subunit consisting of antiparallel N-terminal (residues 30-80) and C-terminal (residues 107-147) helices connected by a 26 residue loop (residues 81-106). The N-terminal helices of each subunit form a parallel coiled-coil structure in the interior of the complex which is surrounded by the C-terminal helices located on the exterior of the complex. The loop region is ordered and displays numerous intermolecular and non-sequential intramolecular contacts. The helical core of SIV e-gp41 is similar to recent X-ray structures of truncated constructs of the helical core of HIV-1 e-gp41. The present structure establishes unambiguously the connectivity of the N- and C-terminal helices in the trimer, and characterizes the conformation of the intervening loop, which has been implicated by mutagenesis and antibody epitope mapping to play a key role in gp120 association. In conjunction with previous studies, the solution structure of the SIV e-gp41 ectodomain provides insight into the binding site of gp120 and the mechanism of cell fusion. The present structure of SIV e-gp41 represents one of the largest protein structures determined by NMR to date.
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PMID:Three-dimensional solution structure of the 44 kDa ectodomain of SIV gp41. 970 17

An RNA 'kissing' complex is formed by the association of two hairpins via base pairing of their complementary loops. This sense-antisense RNA motif is used in the regulation of many cellular processes, including Escherichia coli ColE1 plasmid copy number. The RNA one modulator protein (Rom) acts as a co-regulator of ColE1 plasmid copy number by binding to the kissing hairpins and stabilizing their interaction. We have used heteronuclear two-dimensional NMR spectroscopy to map the interface between Rom and a kissing complex formed by the loop of the trans -activation response (Tar) element of immunodeficiency virus 1 (HIV-1) and its complement. The protein binding interface was obtained from changes in amide proton signals of uniformly 15N-labeled Rom with increasing concentrations of unlabeled Tar-Tar*. Similarly, the RNA-binding interface was obtained from changes in imino proton signals of uniformly 15N-labeled Tar with increasing concentrations of unlabeled Rom. Our results are in agreement with previous mutagenesis studies and provide additional information on Rom residues involved in RNA binding. The kissing hairpin interface with Rom leads to a model in which the protein contacts the minor groove of the loop-loop helix and, to a lesser extent, the major groove of the stems.
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PMID:Mapping of a protein-RNA kissing hairpin interface: Rom and Tar-Tar*. 975 38

The capsid domain of retroviral Gag proteins possesses a single highly conserved subdomain termed the major homology region (MHR). While the mutagenesis of residues in the MHR will impair virus infectivity, the precise solution structure and function of the MHR is not known. To aid the structure/function characterization of the MHR, the structures of synthetic peptides encompassing the MHR of the human immunodeficiency virus type I (HIV-1) and Moloney murine leukemia virus (MoMLV) capsid proteins were investigated by several techniques. Homology-based secondary-structure prediction suggested that the HIV-1 and MoMLV peptides could form 50% and 38% alpha-helix, respectively. CD studies indicated that, in the presence of 50% trifluoroethanol, the HIV-1 peptide adopts an alpha-helical structure over half of its length, while the MoMLV peptide is over one third alpha-helix. Further analysis by 1H-NMR suggested that the C-terminal portion of the MHR of each virus forms a helix in aqueous solution. Distance-geometry structures of each peptide were calculated from NOE distance restraints and were refined by restrained molecular dynamics. The C-terminal halves of both peptides were observed to be in an alpha-helical conformation, while the N-terminal halves were disordered. Furthermore, both helices were amphipathic with high conservation of amino acid side-chain character, suggesting that a conserved helical MHR C-terminus is essential to retroviral capsid protein function.
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PMID:Solution structures of human immunodeficiency virus type 1 (HIV-1) and moloney murine leukemia virus (MoMLV) capsid protein major-homology-region peptide analogs by NMR spectroscopy. 979 4

Recently, we have described the design and characterization of oligonucleotides containing only G and T bases, i.e. T30695 and T30177, that are potent inhibitors of human immunodeficiency virus type 1 (HIV-1) replication in culture (Jing, N., Rando, R. F., Pommier, Y., and Hogan, M. E. (1997) Biochemistry 36, 12498-12505). To understand that observation and to rationalize the generally high thermal stability of oligonucleotide folding for these compounds, we have used NMR methods, coupled to molecular modeling, to obtain a high resolution structure model for T30695, which is the most potent of the integrase inhibitors that have been identified thus far. Modeling and NMR data obtained in the presence of Li+ ions show that T30695 assumes an intramolecular fold with a distorted G-octet core and a set of three open, partially disordered loops. This is referred to as Li+-form structure. The NMR-based model suggests that, upon coordination with three K+ equivalents, the central G-octet becomes more regular and that the loop domains become orderly and compact. This is referred to as K+-form structure. Based upon the assay of inhibition of HIV-1 integrase, T30695 demonstrated a strong inhibition of HIV-1 integrase activity as the K+-form structure, but a poor inhibition of HIV-1 integrase activity as the Li+-form structure. The structure/activity analysis suggests that the K+-induced conformation transition of the tetrad-forming oligonucleotides, such as T30695 and T30177, plays a key role in inhibition of HIV-1 integrase activity.
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PMID:Structure-activity of tetrad-forming oligonucleotides as a potent anti-HIV therapeutic drug. 985 31

We report the design, synthesis and antiviral evaluation of a series of lipophilic, masked phosphoramidate derivatives of the anti-human immunodeficiency virus (HIV) nucleoside analogue d4T, designed to act as membrane-soluble prodrug forms for the free nucleotide. In particular, we report a series of 12 novel compounds with systematic variation in the structure of the carboxylate ester function. In order to rationalize the changes in antiviral action with variation of this moiety we applied our recently developed 31P NMR-based assay for carboxyesterase lability to this series. However, no clear positive correlation emerged, indicating that, at least within this series, factors other than simple esterase lability may be the major determinants of antiviral potency.
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PMID:Synthesis, anti-human immunodeficiency virus activity and esterase lability of some novel carboxylic ester-modified phosphoramidate derivatives of stavudine (d4T). 986 85

The cytokine tumour necrosis factor alpha (TNF-alpha) has been shown to play a role in human immunodeficiency virus (HIV) replication by activating transcription of the provirus in both T cells and macrophages. Therefore, agents that block TNF-alpha-induced HIV expression could have therapeutic value in the treatment of AIDS. We have sought to identify antiviral agents that block TNF-alpha induction of HIV LTR-directed transcription, using a cell-based, virus-free assay system in automated high-throughput screening. HeLa cells were transfected with an HIV LTR-luciferase reporter plasmid and a stable line was isolated in which TNF-alpha increased luciferase production by two- to threefold. This cell line was used to screen approximately 15,000 fungal extracts. An inhibitory activity specific for TNF-alpha-induced HIV LTR transcription was observed in culture OS-F67406. The active component was isolated and identified as a known metabolite, 3-O-methylviridicatin, by NMR and mass spectrometry. No biological activity has been associated with this compound previously. This compound blocks TNF-alpha activation of the HIV LTR in the HeLa-based system, with an IC50 of 5 microM, and inhibited virus production in the OM-10.1 cell line, a model of chronic infection responsive to induction by TNF-alpha, with an IC50 of 2.5 microM.
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PMID:Isolation and characterization of the fungal metabolite 3-O-methylviridicatin as an inhibitor of tumour necrosis factor alpha-induced human immunodeficiency virus replication. 987 86

A series of novel 1-aryl-3-methyl-1H,3H-thiazolo[3,4-a]benzimidazoles, TBZ analogues, were synthesized and investigated as anti-human immunodeficiency virus (HIV) agents in order to study the effects of structural modifications on antiviral activity and cytotoxicity. They were proved to inhibit significantly HIV-1 replication in vitro without showing inhibitory activity on HIV-2 or simian immunodeficiency virus. Their potency was influenced by the presence of suitable substituents in the phenyl ring at C-1 as well as by their stereochemical characteristics. In fact, the most active compound of the series was the trans-1-(2,6-difluorophenyl)-3-methyl-1H,3H-thiazolo[3,4- a]benzimidazole, in which the butterfly-like conformation is stabilized by two intramolecular hydrogen bonds between the fluorine atoms and H-1 and H-3. This was made possible by the trans arrangement of C-1 and C-3 substituents, as shown by X-ray and NMR analysis.
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PMID:Synthesis, structure and in vitro anti-human immunodeficiency virus activity of novel 3-methyl-1H,3H-thiazolo[3,4-a]benzimidazoles. 987 96

The structures of two novel 3'-spiro nucleosides analogues of the potent human immunodeficiency virus type 1 (HIV-1) reverse trancriptase (RT) inhibitor TSAO-m3T, in solution, as derived from NMR spectroscopy are described. In these TSAO analogues the spiro amino oxathioledioxide moiety has been replaced by spiro amino oxazolone or spiro amino oxathiazoledioxide moieties. A comparative study based on theoretical calculations of the hydrophobicity, the solvation free energies and molecular electrostatic potentials (MEP) of the three compounds is also described. No significant conformational differences were detected in solution between TSAO-m3T and its analogues that might account for the differences observed in their inhibitory activity against HIV-1 RT. The calculated hydrophobicity (log P) values, dipole moments and the electrostatic contributions to the solvation free energies of the three spiro ring systems were also similar. However, the differences found in the calculated MEPs of the spiro systems between TSAO-m3T and its analogues suggest that the different electrostatic surroundings of the 4"-amino group of the spiro moiety in the analogues may be responsible for a detrimental electrostatic interaction of the spiro rings with the Glu-B138 of RT.
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PMID:Novel 3'-spiro nucleoside analogues of TSAO-T. Part II. A comparative study based on NMR conformational analysis in solution and theoretical calculations. 987 12

The three-dimensional solution structure of circulin A, a 30 residue polypeptide from the African plant Chassalia parvifolia, has been determined using two-dimensional 1H-NMR spectroscopy. Circulin A was originally identified based upon its inhibition of the cytopathic effects and replication of the human immunodeficiency virus. Structural restraints consisting of 369 interproton distances inferred from nuclear Overhauser effects, and 21 backbone dihedral and nine chi1 angle restraints from spin-spin coupling constants were used as input for simulated annealing calculations and energy minimisation in the program X-PLOR. The final set of 12 structures had mean pairwise rms differences over the whole molecule of 0.91 A for the backbone atom, and 1.68 A for all heavy atoms. For the well-defined region encompassing residues 2-12 and 18-27, the corresponding values were 0.71 and 1.66 A, respectively. Circulin A adopts a compact structure consisting of beta-turns and a distorted segment of triple-stranded beta-sheet. Fluorescence spectroscopy provided additional evidence for a solvent-exposed Trp residue. The molecule is stabilised by three disulfide bonds, two of which form an embedded loop completed by the backbone fragments connecting the cysteine residues. A third disulfide bond threads through the centre of this loop to form a "cystine-knot" motif. This motif is present in a range of other biologically active proteins, including omega-contoxin GVIA and Cucurbita maxima trypsin inhibitor. Circulin A belongs to a novel class of macrocyclic peptides which have been isolated from plants in the Rubiaceae family. The global fold of circulin A is similar to kalata B1, the only member of this class for which a structure has previously been determined.
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PMID:Solution structure by NMR of circulin A: a macrocyclic knotted peptide having anti-HIV activity. 987 10


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