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

The principal neutralizing determinant (PND) of human immunodeficiency virus type 1 (HIV-1) is located in the third hypervariable region (V3) of the virus envelope glycoprotein gp120. The conformation of a V3 peptide of HIV-1IIIB bound to the Fab fragment of an anti-gp120 HIV neutralizing antibody, 0.5beta, was studied by 1H NMR spectroscopy. This 18-residue peptide represents the epitope recognized by 0.5beta and encompasses most of the PND. The slow off-rate of the peptide prevents the observation of peptide/Fab interactions as well as intramolecular interactions within the bound peptide by transferred nuclear Overhauser enhancement (TRNOE). To detect and assign interactions within the bound peptide in the 52 kDa complex, NOESY difference spectra were measured using three strategies: (a) deuteration of peptide residues, (b) Arg two head right arrow Lys replacements, and (c) truncation of the peptide antigen. Each difference spectrum was calculated between NOESY spectra measured for two Fab complexes in which the bound peptides differed in their deuteration or in their sequence. The difference spectra revealed numerous interactions between the N-terminus of the epitope (Arg-4, Lys-5, Ser-6, Ile-7, and Ile-9) and its C-terminus (Phe-17, Val-18, Thr-19, and Ile-20). The assigned NOE interactions within the bound peptide were translated into distance restraints that were used to calculate the conformation of the bound peptide by the hybrid distance geometry/simulated annealing method. A total of 39 long-range (residues i - j >> 4), 14 short-range, and 69 intraresidue NOE interactions within the bound peptide have been assigned. Twelve structures without NOE constraint violations were obtained, having a 1.6 A rms deviation for the backbone atoms. The peptide forms a 10-residue loop, while the two segments flanking this loop, KSI and VTI, interact extensively with each other and possibly form antiparallel beta-strands. This loop conformation could be observed due to the unusual large size (17 residues) of the antigenic determinant recognized by 0.5beta.
 ...
PMID:Conformation of the principal neutralizing determinant of human immunodeficiency virus type 1 in complex with an anti-gp120 virus neutralizing antibody studied by two-dimensional nuclear magnetic resonance difference spectroscopy. 921 8

Polyreactive and thyroglobulin (Tg)-directed proteolytic activities present in the serum IgG of healthy controls and patients with autoimmune disease were studied by electrophoretic separation of 125I-labeled Tg reaction products and spectrofluorometric measurement of Pro-Phe-Arg-methylcoumarinamide cleavage at the Arg-methylcoumarinamide bond. A decrease of the polyreactive proteolytic activity accompanying an increase of the Tg-cleaving activity in IgG from autoimmune thyroiditis (ATh) and systemic lupus erythematosus (SLE) patients was evident. The Tg, a known target of autoimmune reactions in ATh, was cleaved at lower levels by Abs from patients with this disease than from SLE patients. The Tg-cleaving and Tg-binding activities of the autoantibody preparations were not correlated. Enhanced rates of cleavage at saturating substrate concentrations (Vmax), not increased Tg-binding affinities, were evident in IgG preparations with the greatest Tg-cleaving activity. Similarly, diminution of the polyreactive proteolytic activity in IgG from the autoimmune disease patients was due to decreased Vmax values, not decreased substrate-binding affinities. No cleavage of Tg by IgG from subjects with HIV-1 infection, or from mice hyperimmunized with an albumin-hapten conjugate was evident, suggesting that generation of Tg-cleaving Abs does not accompany V region affinity maturation in response to unrelated Ags. These observations establish Tg as a target of catalytic autoantibodies in SLE and ATh, suggest a transition from polyreactive proteolytic activity to autoantigen-directed activity in autoimmune disease, and open the possibility that combining site chemical reactivity is a factor driving the expression of catalytic activity by autoantibodies.
 ...
PMID:Characterization of thyroglobulin-directed and polyreactive catalytic antibodies in autoimmune disease. 923 52

An autolysis-resistant mutant of the HIV-I protease was employed for removal of metabolically stabilized and highly bioactive analogues of bovine growth-hormone-releasing factor (bGRF) from their larger either synthetic or recombinant precursors. The N-terminal four amino acids in two selected model GRF analogues, Y1IDAIFTSSYRKVLAQLSARKLLQDILSRQVF32-OH (I; GRF32) and Y1IDAIFTSSYRKVLAQLSARKLLQDILSRQ30-OH (IA; GRF30), conform well to the specificity of the HIV-I protease for residues in the P1' to P4' positions of its peptide substrates. A variety of amino acids were tried in the N-terminal extension (positions P4-P1) to fit the protease substrate specificity for the 8 amino acids in positions P4-P4'. A synthetic precursor of I, extended N-terminally with RQVF-, a sequence representing the four C-terminal residues in I, was effectively cleaved by the protease at the Phe-1-Tyr1 bond (... RQVF-decreases-YIDA ...) to release GRF32. However, when several soluble fusion proteins linked to GRF32 by the RQVF sequence were expressed in Escherichia coli, attempts to cleave out the core GRF32 met with variable, and only limited, success. By random mutagenesis in a propeptide segment, [MGQSVAQVF]-decreases-GRF30, (II) was identified as a construct that showed reasonably high-level expression in E. coli and was effectively processed by the HIV-I protease. A yield of 5 mg of pure GRF30 was obtained/litre of culture medium after a single HPLC purification step.
 ...
PMID:Use of the HIV-1 protease for excision of growth-hormone-releasing factor from synthetic and recombinant peptide precursors. 926 2

Phenylalanyl-pyrrolidine-2 nitrile (Phe-pyrr-2-CN) and arginyl(PMC)-pyrrolidine-2-nitrile (Arg(PMC)-pyrr-2-CN) are two dipeptidyl peptidase IV/CD26 (DPP-IV/CD26) inhibitors designed and synthesized by our group. These two compounds suppress the enzymatic activity of DPP-IV/CD26 in a competitive and reversible manner. Pretreatment of CEM cells with either of the compounds yielded a marked albeit transient reduction of HIV infection, as measured by HIV1 p24 production, RT activity and syncytium formation. The ID50 value of the Phe-Pyrr-2-CN and Arg(PMC)-pyrr-2-CN in HIV1 inhibition was 5.3 microM and 2.4 microM, respectively. Administration of either of the DPP-IV/CD26 inhibitors 1 h after HIV1 infection did not suppress HIV1 production. An analog whose inhibitory activity toward DPP-IV/CD26 was abolished by blocking the N-terminal of Phe-pyrr-2-CN with the 9-fluorenymethyloxycarbonyl (Fmoc) group had no effect on HIV1 infection. An additive effect of HIV1 inhibition was observed in combinations of either of the DPP-IV/CD26 inhibitors with CD4 monoclonal antibody. These results suggest that DPP-IV/CD26 enzymatic activity may play a role in facilitating HIV1 infection of human CD4+T cells at the entry process. DPP-IV/CD26 inhibitors may therefore have potential use in combination with other drugs to prevent HIV1 transmission.
 ...
PMID:Inhibition of human immunodeficiency virus type 1 infection in a T-cell line (CEM) by new dipeptidyl-peptidase IV (CD26) inhibitors. 927 76

EH is a recently identified protein-protein interaction domain found in the signal transducers Eps15 and Eps15R and several other proteins of yeast nematode. We show that EH domains from Eps15 and Eps15R bind in vitro to peptides containing an asparagine-proline-phenylalanine (NPF) motif. Direct screening of expression libraries with EH domains yielded a number of putative EH interactors, all of which possessed NPF motifs that were shown to be responsible for the interaction. Among these interactors were the human homolog of NUMB, a developmentally reguated gene of Drosophila, and RAB, the cellular cofactor of the HIV REV protein. We demonstrated coimmunoprecipitation of Eps15 with NUMB and RAB. Finally, in vitro binding of NPF-containing peptides to cellular proteins and EST database screening established the existence of a family of EH-containing proteins in mammals. Based on the characteristics of EH-containing and EH-binding proteins, we propose that EH domains are involved in processes connected with the transport and sorting of molecules within the cell.
 ...
PMID:Binding specificity and in vivo targets of the EH domain, a novel protein-protein interaction module. 930 39

This study was undertaken to determine if human recombinant growth hormone (hrGH, 6 mg/d for 2 wk) would stimulate muscle protein synthesis in AIDS wasting. Healthy controls were compared with patients who were HIV+, had AIDS without weight loss, and had AIDS with > 10% weight loss. Before hrGH, rates of skeletal muscle protein synthesis, measured with l-[2H5]phenylalanine, were the same in controls and in all stages of disease. Rates of myofibrillar protein degradation, however, assessed from urinary excretion of 3-methyl histidine, were higher in AIDS and AIDS wasting than in HIV+ or healthy individuals. The group with weight loss had significantly higher TNFalpha levels but not higher HIV viral loads. Muscle function, as determined by isokinetic knee extension and shoulder flexion, was significantly higher in controls than all infected individuals. After GH, rates of protein synthesis were stimulated 27% in controls, with a smaller increase (11%) in HIV+, and a significant depression (42%) in AIDS with weight loss, despite fourfold elevation in insulin-like growth factor-I in all groups. There was a significant correlation of hrGH-induced changes in muscle protein synthesis with severity of disease (P = 0.002). The results indicate increased basal muscle protein degradation and decreased responsiveness of muscle protein synthesis to GH in the later stages of disease.
 ...
PMID:Responsiveness of muscle protein synthesis to growth hormone administration in HIV-infected individuals declines with severity of disease. 932 79

Fluorine nuclear magnetic resonance studies of the cleavage of peptides containing a 4-fluorophenylalanine (FPhe)-Pro bond have been performed in order to determine the conformational specificity of FPhe-Pro bond cleavage by pepsin. The peptides selected were substrates of HIV protease or of avian sarcoma virus protease, both of which have been reported to be cleaved specifically at X-Pro by pepsin as well as by the corresponding viral protease enzyme. By working at 0 degrees C, it was possible to separate kinetically cleavage and cis/trans isomerization. For the case of the protease substrate, Ser-Gln-Asn-FPhe-Pro-Ile-Val-Gln, cleavage was shown to be specific for the trans conformation. A value for the rate constant for hydrolysis of the trans peptide divided by the Michaelis constant, ktH/KMtrans = 0.3 min-1 mM-1 was obtained with this substrate, and the Michaelis constant appears to be considerably higher than the substrate concentration, 3.7 mM, used in the study. On a slower time scale, additional cleavages can readily be detected. For the avian leukemia virus protease substrate, Thr-Phe-Gln-Ala-FPhe-Pro-Leu-Arg-Glu-Ala, the cleavage was both slower and less specific. In addition to the primary cleavage at the FPhe-Pro site, cleavage also occurs at the Ala-FPhe bond on a somewhat slower time scale. In addition to the conformational specificity of the cleavage reaction, these results indicate that pepsin is a better model for HIV protease than for avian leukemia virus protease.
 ...
PMID:Cleavage of the X-Pro peptide bond by pepsin is specific for the trans isomer. 934 Dec 12

The V3 loop consensus motif. Arg-Gly-Pro-Gly-Arg-Ala-Phe-Val-Thr-Ile (HIV-1 IIIB), inhibits an interaction of HIV with CD4-positive lymphocytes. Recently, both proline-rich peptides and peptides containing proline-glycine loops (beta-turns) form a complex with ristocetin dimers. These peptides interact with ristocetin-loaded platelet membrane glycoprotein (GP) Ib and act as inhibitors of von Willebrand factor (vWF)-GPIb interaction by preventing the subsequent formation of ristocetin dimer bridges. The Pro-Gly sequence is also present in the V3 loop consensus motif, Arg-Gly-Pro-Gly-Arg-Ala-Phe-Val-Thr-Ile (HIV-1 IIIB). In this report, we have evaluated the effect of the HIV-1 IIIB peptide on vWF binding to GPIb. This peptide only inhibited vWF binding to GPIb as well as platelet aggregation in the presence of ristocetin while it had no effect on botrocetin-mediated vWF interaction with platelets. The peptide inhibited a binding of anti-vWF monoclonal antibody (RG-46) to immobilized vWF. Furthermore, ristocetin inhibited the binding of HIV-1 IIIB peptide to immobilized CXC-chemokine receptor-4 (CXCR-4) peptide. These results indicate that ristocetin may prevent HIV infection and would be useful a tool to understand the mechanism of HIV tissue tropism and infection.
 ...
PMID:Synthetic peptide from the V3 loop consensus motif with a potent anti-HIV activity inhibits ristocetin-mediated vWF-GPIb interaction. 939 27

Previously our laboratory constructed an HIV-1 which stably maintained a primer binding site (PBS) complementary to tRNA(His) by mutating the region of the provirus within U5 postulated to interact with the anticodon of tRNA(His) (J. Wakefield, S-M Kang, and C. D. Morrow, 1996, J. Virol, 70, 966-975). From the analysis of the virus obtained after long-term culture, we identified an unusual proviral DNA in which the U5-PBS region contained a dual PBS complementary to tRNA(Gly) and tRNA(His), respectively, separated by a 21-nucleotide intervening sequence. To determine if this U5-PBS region containing the dual PBS would give rise to an infectious virus, the mutant U5-PBS containing the dual PBS was subcloned into an infectious HIV-1 proviral clone, pHXB2; the resultant proviral DNA was designated as pHXB2(Gly-His). Transfection of pHXB2(Gly-His) into cells gave rise to infectious virus. Analysis of the U5-PBS region revealed that the virus stably maintained the dual PBS rather than revert back to the wild-type PBS. In addition to genomes with the PBS complementary to tRNA(Gly) and tRNA(His), proviral genomes were identified after extended in vitro culture which contained dual PBS complementary to tRNA(Gly) and tRNA(Phe). To determine which PBS could be used for reverse transcription, we utilized an endogenous reverse transcription/PCR method which could discriminate (based on molecular size of the products) between the minus strand DNA initiated from the two PBSs. The results of this assay demonstrated that either the PBS complementary to tRNA(Gly) or tRNA(His) could be used for the initiation of reverse transcription. The results of our study highlight the complex interrelationship between U5-PBS and primer tRNA required for positioning the tRNA at the PBS and provides new insights into how the tRNA primer used to initiate reverse transcription is selected.
 ...
PMID:Insights into the interaction between tRNA and primer binding site from characterization of a unique HIV-1 virus which stably maintains dual PBS complementary to tRNA(Gly) and tRNA(His). 940 Jun

In previous studies we demonstrated that a synthetic peptide corresponding to the sequence in the (307-330) region of the gp120 principal neutralizing domain of the HIV-1 MN strain is able to bind sCD4 in an affinity chromatography assay and to enhance CD4 expression, CD4 affinity for gp120, and HIV-1 infection. This paper describes a photo affinity labeling experiment, designed to confirm the gp120 peptide-CD4 interaction and to locate the binding site of the synthetic peptide on the CD4 molecule. To this end two specifically marked analogues of the peptide patterned on the (307-330) region of HIV-MN-gp120, in which the TyrI residue is replaced with Phe(p-N3) or Phe(p-NO2), have been synthesized. Irradiation of CD4 solutions in the presence of both analogues produced a new component, the mass value of which confirms the formation of a covalent bond between the peptide and the protein.
 ...
PMID:Investigations using photo affinity labeled analogues confirm the binding between sCD4 and the PND of HIV-1, MN. 942 15


<< Previous 1 2 3 4 5 6 7 8 9 10