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 gene coding for the major capsid protein of feline immunodeficiency virus (FIV) has been cloned into the expression vector pQE60, which allows protein purification by affinity chromatography on a nitrilotriacetic acid/Ni/agarose column. The gene was expressed in Escherichia coli and the resultant soluble protein (FIV-rp24) purified to electrophoretic homogeneity. The amino-acid composition of the recombinant protein is almost identical to that predicted from the DNA sequence. This protein has two tryptophan residues at positions 40 and 126 that have been replaced by phenylalanine by site-directed mutagenesis to obtain two single mutants and a double mutant. Circular dichroism and fluorescence spectroscopy were employed to study the structural features of FIV-rp24 protein and its tryptophan mutants. The analysis of the CD spectra indicated that alpha-helix is the major secondary structural element (48-52%) and that the overall three-dimensional structure is not modified by the mutations. The fluorescence emission spectra showed that both tryptophan residues occupy a highly hydrophobic environment. Moreover, the different tyrosine fluorescence intensities of wild-type and mutant proteins are indicative of the existence of resonance energy transfer processes to nearby tryptophan. The individual contributions of each tryptophan residue to the spectroscopic properties of the wild-type protein were obtained from the spectra of all these proteins. Thermal denaturation studies indicate that the two tryptophan residues do not contribute equally to the stabilization of the three-dimensional structure.
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PMID:Circular dichroism and fluorescence spectroscopic properties of the major core protein of feline immunodeficiency virus and its tryptophan mutants. Assignment of the individual contribution of the aromatic sidechains. 1058 5

WHI-07, a novel bromo-methoxy-substituted aryl phosphate derivative of zidovudine (ZDV), is a potent dual-function contraceptive agent. Although the bromo-methoxy functional groups in the thymine ring of its ZDV are very important for its sperm-immobilizing activity (SIA), the importance of the esterification of the phosphate group with an amino acid side chain and the identity of the para substituent in the aryl moiety remain unclear. In the present study, we have synthesized 23 new analogues of WHI-07 by replacing the alanine (Ala) side chain with different amino acids containing nonpolar side chains, namely tryptophan (Trp), proline (Pro), phenylalanine (Phe), leucine (Leu), methionine (Met), valine (Val), or glycine (Gly). The para substituents on the aryl moiety included bromo, chloro, fluoro, nitro, or methoxy groups. The SIA of each of the 23 WHI-07 analogues was evaluated by computer-assisted sperm analysis. The potential cytotoxicity of these compounds against normal human ectocervical and endocervical epithelial cells was evaluated using MTT (3-[4, 5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) cell viability assays. The replacement of the Ala side chain of WHI-07 with Val, Leu, or Phe led to a complete loss of SIA (EC(50) values > 500 microM), whereas replacement with Trp reduced the SIA by 4-fold. The presence of para substituents on the phenyl moiety led to significant alterations in SIA. The anti-human immunodeficiency virus (HIV) activity of Trp-containing WHI-07 analogues was also diminished. Our finding highlights the necessity of Ala side chain and the presence of electron-withdrawing para-bromo substituent on the phenyl moiety in addition to bromo-methoxy functionalization groups on the thymine ring in order for the phosphoramidate derivatives of ZDV to be effective dual-function spermicidal agents. Unlike the detergent-type microbicide, nonoxynol-9, which was cytotoxic to normal human ectocervical and endocervical epithelial cells (IC(50) values of 22 microM and 16 microM, respectively) at spermicidal concentrations (EC(50) = 81 microM), WHI-07 and its active analogues were selectively spermicidal without cytotoxicity against female genital tract epithelial cells. WHI-07 and its Trp analogues hold particular clinical promise for the development of novel, nondetergent-type prophylactic contraceptives for the prevention of heterosexual HIV/acquired immunodeficiency syndrome transmission.
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PMID:Structural requirements for potent human spermicidal activity of dual-function aryl phosphate derivative of bromo-methoxy zidovudine (compound WHI-07). 1061 Oct 65

Accelerated apoptosis is one mechanism proposed for the loss of CD4+ T-lymphocytes in human immunodeficiency virus type 1 (HIV-1) infection. The HIV-1 envelope glycoprotein, gp160, contains two C-terminal calmodulin-binding domains. Expression of gp160 in Jurkat T-cells results in increased sensitivity to FAS- and ceramide-mediated apoptosis. The pro-apoptotic effect of gp160 expression is blocked by two calmodulin antagonists, tamoxifen and trifluoperazine. This enhanced apoptosis in response to FAS antibody or C(2)-ceramide is associated with activation of caspase 3, a critical mediator of apoptosis. A point mutation in the C-terminal calmodulin-binding domain of gp160 (alanine 835 to tryptophan, A835W) eliminates gp160-dependent enhanced FAS-mediated apoptosis in transiently transfected cells, as well as in vitro calmodulin binding to a peptide corresponding to the C-terminal calmodulin-binding domain of gp160. Stable Tet-off Jurkat cell lines were developed that inducibly express wild type gp160 or gp160A835W. Increasing expression of wild type gp160, but not gp160A835W, correlates with increased calmodulin levels, increased apoptosis, and caspase 3 activation in response to anti-FAS treatment. The data indicate that gp160-enhanced apoptosis is dependent upon calmodulin up-regulation, involves the activation of caspase 3, and requires calmodulin binding to the C-terminal binding domain of gp160.
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PMID:Requirement of calmodulin binding by HIV-1 gp160 for enhanced FAS-mediated apoptosis. 1062 68

In a systematic search for developing a virucidal spermicide with potent anti-human immunodeficiency virus (HIV) and spermicidal activities, we synthesized and evaluated 14 phosphoramidate derivatives of 5-bromo-6-methoxy-zidovudine (PP-BMZ) with differing amino acid ester side chains and para substitutions on the phenyl moiety. Anti-HIV activity was tested by measuring viral p24 antigen production as a marker of viral replication in HIV-1-infected human peripheral blood mononuclear cells. The effect of various PP-BMZ compounds on human sperm motion kinematics was analysed by computer-assisted sperm analysis. Varying the Ala side chain of the phosphoramidate group to other non-polar amino acids, including the cyclic amino acids proline and tryptophan, led to significant alterations in both anti-HIV and spermicidal activities. Our findings highlight the necessity of the Ala side chain and the presence of an electron-withdrawing para-bromo substituent on the phenyl moiety in addition to the bromo-methoxy functional groups on the thymine ring for the PP-BMZ compounds to be effective virucidal spermicides. These membrane permeable dual-function nucleoside analogues may provide the basis for a new strategy aimed at prevention of the sexual transmission of HIV while providing fertility control for women.
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PMID:Importance of the alanine methyl ester side chain for the biological activity profile of dual-function phenyl phosphate derivatives of bromo-methoxy-zidovudine. 1069 52

Using synthetic inhibitors, it has been shown that the ectopeptidase dipeptidyl peptidase IV (DP IV) (CD26) plays an important role in the activation and proliferation of T lymphocytes. The human immunodeficiency virus-1 Tat protein, as well as the N-terminal nonapeptide Tat(1-9) and other peptides containing the N-terminal sequence XXP, also inhibit DP IV and therefore T cell activation. Studying the effect of amino acid exchanges in the N-terminal three positions of the Tat(1-9) sequence, we found that tryptophan in position 2 strongly improves DP IV inhibition. NMR spectroscopy and molecular modeling show that the effect of Trp(2)-Tat(1-9) could not be explained by significant alterations in the backbone structure and suggest that tryptophan enters favorable interactions with DP IV. Data base searches revealed the thromboxane A2 receptor (TXA2-R) as a membrane protein extracellularly exposing N-terminal MWP. TXA2-R is expressed within the immune system on antigen-presenting cells, namely monocytes. The N-terminal nonapeptide of TXA2-R, TXA2-R(1-9), inhibits DP IV and DNA synthesis and IL-2 production of tetanus toxoid-stimulated peripheral blood mononuclear cells. Moreover, TXA2-R(1-9) induces the production of the immunosuppressive cytokine transforming growth factor-beta1. These data suggest that the N-terminal part of TXA2-R is an endogenous inhibitory ligand of DP IV and may modulate T cell activation via DP IV/CD26 inhibition.
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PMID:Down-regulation of T cell activation following inhibition of dipeptidyl peptidase IV/CD26 by the N-terminal part of the thromboxane A2 receptor. 1089 52

We used intrinsic tryptophan fluorescence to study the nucleocapsid protein from human T-cell leukemia virus-type one, HTLV-1 p15, an 85-amino-acid protein with two Trp-containing zinc-finger motifs. Fluorescence spectra suggested an interaction between the two zinc fingers and another interaction involving the C-terminal tail and the zinc fingers. Titrations with nucleic acid revealed similar, sub-micromolar affinity for poly(dT) and poly(U) in 1 mM sodium phosphate, pH 7. Double-stranded DNA bound an order of magnitude weaker, suggesting helix-destabilizing activity. Base preference of p15 was T approximately U>I approximately C approximately G>A; affinity spanned about one order of magnitude. HTLV-1 p15 bound weaker and with less variation than reported values for either human or simian immunodeficiency virus homologues. The low affinity of p15 for nonspecific nucleic acids distinguishes it from other nucleocapsid proteins, and may suggest its involvement in additional steps of the virus life cycle other than RNA packaging.
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PMID:Fluorescence and nucleic acid binding properties of the human T-cell leukemia virus-type 1 nucleocapsid protein. 1101 30

Cellular (Th1-type) immune response is centrally involved in the pathogenesis of various diseases. Within the immunological cascades of Th1-type immunity, interferon gamma (IFN-gamma), among other cytokines, is critically involved. It triggers a series of immune-relevant reactions mostly directed towards forward regulation of the antigen specific immune response. However, in chronic states of immune activation, systemically increased IFN-gamma is no longer antigen specific and is associated with the development of immunodeficiency. IFN-gamma also stimulates the production of neopterin, a low-mass compound, in human monocytes/macrophages. Accordingly, neopterin concentrations in humans reflect the degree of Th1-type immune activation. Since IFN-gamma also stimulates the release of reactive oxygen species (ROS) from immunocompetents cells, the amount of neopterin produced also serves as an indirect estimate of oxidative stress. In parallel, IFN-gamma activates the degradation of tryptophan, which appears to limit the growth of intracellular pathogens and the proliferation of cells, including T lymphocytes. Thus, during persisting states of immune activation, the production of IFN-gamma is not only associated with forward regulation of the immune response, but also with immunosuppressive mechanisms. The increased formation of neopterin and degradation of tryptophan may result in a decreased T cell responsiveness and development of immunodeficiency.
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PMID:Cellular immune activation, neopterin production, tryptophan degradation and the development of immunodeficiency. 1105 41

Several chemokine receptors (CKRs) act as coreceptors of human immunodeficiency virus type 1 (HIV-1), type 2 (HIV-2) and simian immunodeficiency virus (SIV). These CKRs interact with the V3 domain of the envelope (env) protein of HIV/SIV. In this study, we found that the amino acid sequences of two chemokines (SDF-1beta and RANTES), whose receptors (CXCR4 and CCR5) act as major coreceptors for HIV-1, HIV-2 or SIV, showed statistically significant similarity to those of the region containing the third variable (V3) and the third conserved (C3) domains (the V3--C3 domain) of the env protein of HIV-1 and HIV-2. We made a multiple alignment of amino acid sequences for 24 chemokines and the region encompassing the second conserved (C2), V3 and C3 domains (the C2--V3--C3 region) of 10 strains of HIV/SIV. Surprisingly, the hydropathic profile and several important amino acids for protein conformation, such as cysteine and tryptophan, are remarkably conserved between chemokines and the V3--C3 region of HIV/SIV. Moreover, hydrophobic amino acids, such as leucine, isoleucine and valine, are found to be clustered both in the amino-terminal region of chemokines and the C2 domain of HIV/SIV. Thus, chemokines have significantly similar profiles of amino acid properties to those of the C2--V3--C3 region of the env protein of HIV/SIV. These findings raise a hypothesis that chemokines and the C2--V3--C3 region have a common origin. Namely, the HIV/SIV ancestor incorporated a chemokine gene into its env gene. The captured chemokine gene has rapidly diverged by frequent mutations specific to the retroviral genome, and thereby obtained the ability to interact with various CKRs in a short period of time. This paper proposes that the capture of a ligand gene of the host cells into the viral genome may be one of the important mechanisms of viral evolution to expand its host range and generate new viral species.
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PMID:How can human and simian immunodeficiency viruses utilize chemokine receptors as their coreceptors? 1116 77

The binding of NCp7, the nucleocapsid protein of human immunodeficiency virus type 1, to oligonucleotide stem--loop (SL) sequences of the genomic Psi-recognition element has been studied using fluorescence, phosphorescence, and optically detected magnetic resonance (ODMR). RNA SL2, SL3, and SL4 constructs bind with higher affinity than the corresponding DNAs. G to I substitutions in the SL3 DNA loop sequence lead to reduced binding affinity and significant changes in the triplet state properties of Trp37 of NCp7, implicating these bases in contacts with aromatic amino acid residues of the zinc finger domains of NCp7, in agreement with the NMR structure of the 1:1 complex of NCp7 and SL3 RNA [DeGuzman, R. N., Wu, Z. R., Stalling, C. C., Pappaladro, L., Borer, P. N., and Summers, M. F. (1998) Science 279, 384-388]. The NCp7 to SL binding stoichiometry is 2:1 for intact SL sequences but is reduced to 1:1 for SL variants with an abasic or hydrocarbon loop. It is proposed that Delta D/Delta E(0,0), where Delta D is the change in the zero-field splitting D parameter and Delta E(0,0) is the shift of the tryptophan phosphorescence origin, provides a measure of aromatic stacking interactions with nucleic acid bases. Values on the order of 10(-5) indicate significant stacking interactions, while values closer to 10(-6) result from interactions not involving aromatic stacking. Binding of NCp7 to oligonucleotide substrates produces shortened Trp37 triplet state lifetimes by enhancement of k(x) and an increase of the relative value of P(x), the intersystem crossing rate to the T(x) sublevel. These effects are attributed to a reduction in the degree of electronic symmetry of Trp37 in the complexes. Guanine and adenine triplet states produced by optical pumping of SL3 DNA are characterized. We find, as with tryptophan, that D < 3E.
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PMID:Phosphorescence and optically detected magnetic resonance of HIV-1 nucleocapsid protein complexes with stem-loop sequences of the genomic Psi-recognition element. 1117 Apr 68

Circular dichroism and fluorescence spectroscopy have been employed to study the urea unfolding mechanism of a recombinant form of the major core protein of feline immunodeficiency virus (FIV-rp24) and its native tryptophan mutants. The equilibrium denaturation curves indicate the existence of two transitions. The first unfolding transition most likely reflects the denaturation of the carboxy-terminal region of FIV-rp24. Consequently, the second transition, where the changes in fluorescence are produced, should reflect the denaturation of the amino-terminal region. If the intermediate observed upon urea denaturation is an on-pathway species, the data described herein can reflect the sequential and independent loss of structure of the two domains that this type of proteins possesses.
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PMID:Urea equilibrium unfolding of the major core protein of the retrovirus feline immunodeficiency virus and its tryptophan mutants. 1125 11


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