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: EC:3.4.21.4 (trypsin)
42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Results obtained by using a reconstitution technique on the Sendai virus envelope confirm that cleavage of one of the envelope glycoproteins (GP2) is prerequisite for activation of hemolytic and cell fusion activities of Sendai virus. The cleavage of GP2 occurs even when free envelope subunits are directly treated with trypsin in the presence of detergent. Trypsin treatment, either of the reconstituted particle or of the free envelope subunits but not of the intact virion, also causes a cleavage of the largest envelope glycoprotein (GP1), suggesting that a site on GP1 sensitive to trypsin becomes exposed during solubilization and reconstitution. The latter cleavage, however, is not associated with any changes in biological activities.
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PMID:Trypsin action on the growth of Sendai virus in tissue culture cells. IV. Evidence for activation of sendai virus by cleavage of a glycoprotein. 17 21

A novel membrane-bound serine esterase in cultured human T4+ lymphocytes, recently purified and named tryptase TL2, binds specifically to the external envelope protein gp 120 of HIV-1, interacting with its V3 domain. This binding was selectively blocked by inhibitors of tryptase TL2 with a GPCR sequence in their reactive site, synthetic peptides corresponding with the sequences of the V3 domains of various HIV-1 strains with the GPGR sequence, and antibody against tryptase TL2, or neutralizing antibody against the V3 domain of HTLV-IIIB. These findings suggest that tryptase TL2 is a binding protein of the V3 domain of HIV-1 envelope glycoprotein.
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PMID:Tryptase TL2 in the membrane of human T4+ lymphocytes is a novel binding protein of the V3 domain of HIV-1 envelope glycoprotein gp 120. 167 98

A novel membrane-bound serine esterase, named tryptase TL2, which is immunologically reactive with the antibody inhibiting induction of syncytia by human immunodeficiency virus-1 (HIV-1) (HATTORI, T., KOITO, A., TAKATSUKI, K., KIDO, H., and KATUNUMA, N., 1989, FEBS Lett., 248, 48-52), has been purified from a human T4+ lymphocyte clone. The enzyme has a molecular mass of 198 +/- 15 kDa, and is composed of two subunits of 32 kDa and four subunits of 28 kDa. The enzyme was strongly inhibited by the envelope glycoprotein gp120 of HIV-1, by synthetic peptides of V3 domains of gp120 s with the sequence GPGR in their center, which correspond to the principal neutralizing epitopes of the gp120s of various HIV-1 strains, by Kunitz-type inhibitors with the sequence GPCR in their active site, such as trypstatin, H130, and [Arg15, Glu52] aprotinin and by the microbial inhibitors leupeptin and antipain. This enzyme was specifically bound to the inhibitor V3 domain of gp120 of HIV-1, and this binding was blocked by the inhibitors of tryptase TL2, with a central motif GPCR or GPGR sequence in their center, but not by leupeptin and antipain without the motif. These findings suggest that tryptase TL2 is important in target site recognition and binding of HIV-1 in co-operation with CD4 receptor in the initial process of HIV-1 infection.
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PMID:A novel membrane-bound serine esterase in human T4(+)-lymphocytes is a binding protein of envelope glycoprotein gp120 of HIV-1. 168 71

By the use of limited trypsin digestion of purified virions, we generated a membrane anchor-free and crystallizable form of the tick-borne encephalitis virus envelope glycoprotein E. It retained its reactivity with a panel of monoclonal antibodies, and only subtle structural differences from the native protein E were recognized. Treatment with the bifunctional cross-linker dimethylsuberimidate resulted in the formation of a dimer. Crystallization experiments yielded hexagonal rod-shaped crystals suitable for X-ray diffraction analysis.
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PMID:The flavivirus envelope protein E: isolation of a soluble form from tick-borne encephalitis virus and its crystallization. 171 95

The CD4 molecule is known to be the preferential receptor for the HIV-1 envelope glycoprotein. Epidermal Langerhans cells are dendritic cells which express several surface antigens, among them CD4 antigens. To clarify the exact role of CD4 molecules in Langerhans cell infection induced by HIV-1, we investigated the possible involvement of the interactions between HIV-1 gp 120 or HIV-1 gp 160s (soluble gp 160) and Langerhans cell surface. We also assessed the expression of CD4 molecules on Langerhans cell membranes dissociated by means of trypsin from their neighbouring keratinocytes. The cellular phenotype was monitored using flow cytometry and quantitative immunoelectron microscopy. We reported that human Langerhans cells can bind the viral envelope proteins (gp 120 or gp 160s), and that this binding does not depend on CD4 protein expression. This binding is not blocked by anti-CD4 monoclonal antibodies. We show that a proportion of gp 120/gp 160s-receptor complexes enters Langerhans cells by a process identified as a receptor-mediated endocytosis. The amount of surface bound gp 120/gp 160s is not consistent with the amount of CD4 antigens present on Langerhans cell membranes. Gp 120/gp 160s binding sites on Langerhans cell suspensions appeared to be trypsin resistant, while CD4 antigens (at least the epitopes known to bind the HIV-1) are trypsin sensitive. A burst of gp 120 receptor expression was detected on 1-day cultured Langerhans cells while CD4 antigens disappeared. These findings lead to the most logical conclusion that binding of gp 120/gp 160s is due to the presence of a Langerhans cell surface molecule different from CD4 antigens.
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PMID:Interaction of human epidermal Langerhans cells with HIV-1 viral envelope proteins (gp 120 and gp 160s) involves a receptor-mediated endocytosis independent of the CD4 T4A epitope. 172 50

The gp120 envelope glycoprotein of human immunodeficiency virus type 1 binds the cell surface protein CD4 with high affinity. Here we report the use of proteolysis to define regions of gp120 involved in CD4 binding. Cleavage of gp120 with Staphylococcus aureus V8 protease at residue 269 or with trypsin at residue 432 destroys CD4 binding. These same sites are protected from proteolytic cleavage by bound CD4. Cleavages at 64, 144, 166, 172, and 315 do not affect binding and are not protected by bound CD4, indicating that these regions are not critical for binding CD4. All proteolytic fragments found in coprecipitates with CD4 were covalently associated via disulfides and comprised complete gp120 molecules. Previous conclusions by Nygren et al. [Nygren, A., Bergman, T., Matthews, T., Jornvall, H. & Wigzell, H. (1988) Proc. Natl. Acad. Sci. USA 85, 6543-6546] that both large and small (95-kDa and 25-kDa) V8 proteolytic fragments bind CD4, independently, are not distinguished by their experiments from the result found here that the small fragment immunoprecipitates with CD4 while disulfide-linked to the larger fragment.
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PMID:CD4-binding regions of human immunodeficiency virus envelope glycoprotein gp120 defined by proteolytic digestion. 176 44

The CD4 molecule is known to be the preferential receptor for the HIV1 envelope glycoprotein. Epidermal Langerhans cells (LC) are dendritic cells which express several surface antigens, among them the CD4 antigens. LC infection was suggested when these cells were seen to present buddings coincident with membrane thickening of roughly 100 nm in size. These buddings were similar in ultrastructural aspect to HIV buddings on in vitro infected promonocytic cells (U937). To clarify the exact role of CD4 molecules in LC infection induced by HIV1, we investigated the possible involvement of between native and recombinant HIV1 gp120 and the LC surface. We also assessed the expression of CD4 molecules on LC membranes dissociated by means of trypsin from their neighbouring keratinocytes. The cellular phenotype was monitored using flow cytometry. We show that human LC can bind the viral envelope protein and that this binding does not depend on CD4 protein expression. The amount of surface bound gp120 was not consistent with the amount of CD4 antigens present on LC membranes. The gp120-binding sites on LC in suspension appear to be typsin-resistant while the CD4 antigens (at least the epitopes known to bind HIV1) are trypsin-sensitive. A burst of gp120 receptor expression was detected on 1-day cultured LC while the CD4 antigens disappeared. These findings lead to the logical conclusion that the binding of gp120 is due to the presence of a LC surface molecule which is different from CD4 antigens.
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PMID:Trypsin-resistant gp120 receptors are upregulated on short-term cultured human epidermal Langerhans cells. 189 37

The CD4 molecule has several biological functions, physiologically as a receptor for major histocompatibility complex class II molecules on antigen-presenting cells, and pathologically as a receptor for human immunodeficiency virus (HIV) by its binding to the HIV envelope glycoprotein gp 120. The frequency of CD4+ cells has been shown to correlate positively with both susceptibility and cytopathogenic effect by HIV. To determine if CD4 expression varied during the cell cycle, a CD4-expressing monocytoid cell line, U 937 clone 16, was synchronized with regard to cell growth. The CD4 antigen was analysed with regard to expression, density and rate of reappearance after treatment with trypsin, during the different phases of the cell cycle. The CD4 reappearance rate was found to be maximal during the S phase. This was followed by an increased expression and density in the late S/G2 phase. Thus a cell cycle-dependent expression of CD4 molecules on the cell surface was observed.
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PMID:Cell cycle-dependent expression of CD4 antigen in a monocytoid cell line. 192 11

A novel membrane-bound serine esterase, named tryptase TL2, which is immunologically reactive with the antibody inhibiting induction of syncytia by human immunodeficiency virus-1 (HIV-1) (Hattori, T., Koito, A., Takatsuki, K., Kido, H., and Kutunuma, N. (1989) FEBS Lett., 248, 48-52), has been purified from a human T4+ lymphocyte clone. The enzyme has a molecular mass of 198 +/- 15 kDa, as judged by gel-permeation liquid chromatography, and is composed of two subunits of 32 kDa and four subunits of 28 kDa, as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Studies with model peptide substrates showed that the enzyme preferentially recognized L-arginine and cleaved Boc-Gln-Gly-Arg-4-methyl-coumaryl-7-amide and Boc-Gln-Ala-Arg-4-methyl-coumaryl-7-amide with high efficiency at a pH optimum of 8.5. The enzyme was strongly inhibited by the envelope glycoprotein gp 120 of HIV-1, by synthetic peptides with the sequence GPGR in their center, which corresponds to the principal neutralizing epitope of the gp 120s of various HIV-1 strains, by Kunitz-type inhibitors with the sequence GPCR in their active site, such as trypstatin, HI30, and [Arg15, Glu52]aprotinin and by the microbial inhibitors leupeptin and antipain. Studies on the subcellular distribution of tryptase TL2, immunohistochemical analysis, and cell surface radioiodination indicated that the enzyme is mainly localized in the plasma membrane.
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PMID:A novel membrane-bound serine esterase in human T4+ lymphocytes immunologically reactive with antibody inhibiting syncytia induced by HIV-1. Purification and characterization. 197 28

We have studied the specificity requirements for processing of the human insulin proreceptor by successively replacing each basic amino acid in the tetrabasic cleavage site with alanine. These mutated receptor cDNAs have then been overexpressed in Chinese hamster ovary cells, using vectors containing the mouse dihydrofolate reductase gene to amplify the transfected cDNAs in the presence of increasing concentrations of methotrexate. High levels of expression, ranging up to 6 x 10(7) receptors/cell were achieved in these experiments. Replacement of the P1 arginine with alanine led to the complete suppression of processing, as occurs also in a naturally occurring serine mutation at this site (Yoshimasa, Y., Seino, S., Whittaker, J., Kakehi, T., Kosaki, A., Kuzuya, H., Imura, H., Bell, G. I., and Steiner, D. F. (1988) Science 240, 783-787). A small amount of cleavage at alternative sites was detected. Replacement of the P2 arginine or P3 lysine with alanine did not in either case affect conversion to mature alpha and beta subunits, while replacement of the P4 arginine significantly inhibited processing. The binding isotherms for the processed versions of the receptor were comparable to previously published normal values. The unprocessed proreceptor bound insulin normally but was autophosphorylated less efficiently than processed versions of the receptor expressed in the same cells. These results suggest that a single processing protease with trypsin-like specificity may be involved in processing both insulin and insulin-like growth factor-I receptor precursors as well as a variety of viral envelope glycoprotein precursors.
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PMID:Effects of amino acid replacements within the tetrabasic cleavage site on the processing of the human insulin receptor precursor expressed in Chinese hamster ovary cells. 221 23


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