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)

Infection of BHK 21 cells by vesicular stomatitis virus (VSV) results in the intracellular synthesis of the five viral proteins which are easily detectable in polyacrylamide gels after short labeling periods with [35S]methionine. In addition, a 6th prominent radioactive protein band appears intracellularly in VSV-infected BHK cells. This additional polypeptide is also coded by the viral genome, because it is immunoprecipitated by antibodies against viral particles and more specifically by antibodies against purified G-protein. We propose to call this derivative of the G-protein Gsi-protein (short intracellular G-protein). It is associated with intracellular membranes and has an apparent mol. wt. of 58 000. Both G- and Gsi-protein have the same kinetics of appearance in the cell. The ratio of G-:Gsi-protein in BHK 21 cells is approximately 85:15. The mol. wt. difference of approximately 6000 daltons between G- and Gsi-protein is not due to variations in the degree of glycosylation because trypsin digestions of both [3H]mannose-labeled glycoproteins gave rise to identical glycopeptide patterns. Incubation of microsomes with trypsin demonstrates that Gsi-protein is protected in its full length by intracellular membranes. Gsi-protein is lacking an extended carboxy-terminal region of the viral G-protein sequence because it is not modified by palmitic acid and is not immunprecipitated by specific antibodies against a C-terminal peptide of the G-protein. Limited proteolysis by endoproteinase arg C indicates that the structure of Gsi-protein is very similar to the shedded form of the G-protein which has been previously described in the literature.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Intracellular appearance of a glycoprotein in VSV-infected BHK cells lacking the membrane-anchoring oligopeptide of the viral G-protein. 608 25

The infectivity of most rotaviruses is enhanced by treatment with trypsin. We studied the mechanism of enhancement of examining the effect of trypsin on rotavirus infectivity, aggregation, early interactions with host cells, and structure. The results indicated that trypsin does not increase levels of infectious virus by dispersion of aggregates or affect the efficiency or rate of attachment of virus to cells. A fraction of virus that was not infections without trypsin treatment was found to attach to cells, but did not initiate antigen synthesis. When cells were infected with labeled, purified virus, increased levels of uncoated particles were found in cells infected with trypsin-treated virus. Infection of cells with trypsin-treated virus also led to greater levels of RNA synthesis early in the infection. The results suggest that trypsin converts a noninfectious fraction of virus into infectious virus by allowing this fraction to uncoat in the infected cell. Trypsin was found to cleave an 88,000-dalton structural polypeptide of bovine rotavirus generating 67,000- and 20,000-dalton cleavage products.
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PMID:Trypsin enhancement of rotavirus infectivity: mechanism of enhancement. 616 41

The nature of the refractoriness of C6 rat glioma cells to herpes simplex virus type 2 (HSV-2) was examined. Infection of C6 cells with HSV-2 results in low virus yields, not exceeding the input virus. Although virus growth studies suggested a restricted cycle of virus replication, synthesis of HSV-2 DNA and HSV-2-specific antigens could not be detected. In addition, HSV-2 yields in C6 cells were unaffected by interferon, cycloheximide, tunicamycin, actinomycin D and cytosine arabinoside. However, trypsin, but not EDTA, treatment of infected C6 cells at 4 hours postinfection (p.i.) reduced maximal HSV-2 yields at 24 hours p.i. by 61 percent. These data: 1) indicate that HSV-2 fails to replicate in C6 cells and is prohibited from directing the synthesis of virus macromolecules; and 2) suggests that the increment of HSV-2 yields observed during the synthesis phase of the virus growth cycle represents re-envelopment and egress of a portion of the input virus.
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PMID:Abortive infection of neural cells by herpes simplex virus type 2. 629 39

Infection of BHK cells with foot-and-mouth disease virus (FMDV) causes a thorough change in the electrophoretic profile of whole nuclear histones. It consists in the disappearance of histone H3 and the appearance of a new polypeptide (Pi) which migrates between histones H2A and H4 on SDS-polyacrylamide gels. Protein Pi is detected at 2 hr postinfection (pi), the time in which viral RNA synthesis begins to increase, and reaches equimolecular amounts with the remaining core histones 1 hr later, when the disappearance of histone H3 is almost complete. Labeling of cells prior to infection demonstrates that Pi is not a novo product but the result of a viral-induced processing of a host precursor synthetized beforehand. Protein Pi comigrates with histone H2A/B in acetic acid/urea polyacrylamide gels and it shares common major peptides with histone H3 under controlled proteolysis with protease V8 or trypsin. The mononucleosomal and nucleosomal DNA pattern analysis after micrococcal nuclease treatment of nuclei from infected and mock-infected cells did not show any significant differences even though after 3 hr (p.i.), protein Pi replaces histone H3 in the nucleosomal structure. It was concluded that FMDV infection is responsible for a specific modification in the nucleus of infected cells which leads, after 3 hr (p.i.), to a complete histone H3 protein Pi transition in the nucleosomes.
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PMID:Histone H3 modification in BHK cells infected with foot-and-mouth disease virus. 633 Sep 87

Infection with Trichuris muris eggs or Nematospiroides dubius larvae (orally administered) did not affect IgG or IgM antibody responses to 0 X 2 micrograms polyvinyl pyrrolidone (PVP) (intravenously (i.v.) or intraperitoneally (i.p.)) or 20 micrograms PVP (i.p.) in C57BL mice. However, Nippostrongylus brasiliensis L3 subcutaneously (s.c.) and N. dubius L3 (i.v.) significantly increased responses to PVP (i.p.) so migrating larvae are probably responsible. Similar enhancement was obtained when extracts of N. brasiliensis worms or N. dubius larvae were administered i.p. The activity of N. brasiliensis extract was trypsin-insensitive and unaffected by heat (1 h, 60 degrees). Extracts of A. suum did not cause significant enhancement and BALB/c mice were not affected by N. brasiliensis extract. The possible roles of regulatory T-cells, non-specific mitogenesis and macrophage activation are discussed.
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PMID:Immunological consequences of intestinal helminth infections in C57BL mice. Humoral responses to polyvinyl pyrrolidone. 665 43

Cell-free infectious viruses were successfully recovered by the aid of freezing and thawing from cultures infected with the Kitaken-1 and Biken strains of subacute sclerosing panencephalitis (SSPE) virus. Our results including those in a previous report which dealt with the Niigata-1 strain of SSPE virus show that cell-free viruses can be detected from all of the SSPE virus-carrying cultures established in Japan. It was also found that cell-free infectious viruses can be recovered efficiently by dispersing the virus-carrying cultures with EDTA. The inclusion of trypsin in the EDTA solution, however, caused a poor recovery of the infectious viruses. Infection of cells with the cell-free viruses readily established the virus-carrying cultures that have characteristics comparable to those of their original cultures. The culture infected with the Kitaken-1 strain produced infectious viruses in about ten times the amount of the other two infected cultures. The buoyant densities of the cell-free infectious viruses were almost the same among the three strains, the values being 1.120 to 1.132, but significantly less than that of 1.164 of measles virus. The low density can be ascribed to one of the characteristics of these SSPE viruses.
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PMID:Mode of subacute sclerosing panencephalitis (SSPE) virus infection in tissue culture cells. II. Cell-free viruses in cell cultures infected with Kitaken-1 and Biken strains of SSPE virus. 721 4

The mechanisms of entry of Ileal symbiont intracellularis into IEC-18 rat enterocyte cells and subsequent bacterial proliferation were examined in centrifuge-assisted and static infections. Live, oxygen or neomycin damaged, and formalin killed bacteria, each rapidly entered viable cells. Live or damaged bacteria did not enter cells nor proliferate within cells after static infection of cells cooled to 5 degrees C. Infection of cells was greatly reduced at 20 degrees or 32 degrees compared to infection at 37 degrees C. Centrifuge-assisted infection was also reduced by chilling the cells. Cytochalasin D but not B inhibited the entry process indicating an actin-dependent infection, although other pathways may also be involved in centrifuge-assisted infections. Drugs capable of modifying cell membrane charge, heparin receptors or trypsin-labile proteins were all inactive in preventing or enhancing infection. We therefore conclude that infection of enterocytes by IS intracellularis is dependent on host cell activity and actin polymerization, but is independent of bacterial viability.
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PMID:Infection of cultured rat enterocytes by Ileal symbiont intracellularis depends on host cell function and actin polymerisation. 748 47

Infection of cells by human papillomaviruses (HPVs) associated with malignant genital lesions has not been studied because of the lack of an in vitro system and the unavailability of virions. We have now used virus-like particles (VLPs) of HPV type 33 to analyze the initial events in the interaction of the HPV capsid with cell lines. Binding of VLPs to HeLa cells was observed in biochemical assays and by immunofluorescence. VLP binding was inhibited by antisera raised against VLPs but not by monoclonal antibodies recognizing either L1 or L2 epitopes accessible on VLPs. Under saturating conditions, approximately 2 x 10(4) VLPs were bound per cell, with a dissociation constant of about 100 pM. VLPs composed of L1 alone bound as well as VLPs composed of both capsid proteins, indicating that L2 is not required for initial binding. VLPs dissociated into capsomers did not bind, demonstrating that intercapsomer contacts are required. Neither capsomers nor simian virus 40 virions competed with VLP binding. Uptake of VLPs by small and smooth endocytic vesicles was demonstrated by immunoelectron microscopy. Cellular binding of VLPs was sensitive to trypsin but not to sialidase, N-glycosidase, or octyl-beta-D-glycopyranoside treatment, suggesting that a cell surface protein is involved in the VLP binding. Cell lines originating from a variety of tissues and organisms as distantly related as insects and humans bound VLPs with similar efficiency and specificity. Therefore, the putative receptor mediating VLP attachment should be highly conserved and cannot be responsible for the species and tissue specificity of HPVs.
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PMID:Binding and internalization of human papillomavirus type 33 virus-like particles by eukaryotic cells. 774 72

A 5-kDa polypeptide, pseudothionin Solanum tuberosum 1 (Pth-St1), which was active against Clavibacter michiganensis subspecies sepedonicus, a bacterial pathogen of potatoes, has been purified from the buffer-insoluble fraction of potato tubers by salt extraction and HPCL. Pth-St1 was also active against other potato pathogens tested (Pseudomonas solanacearum and Fusarium solani). The N-terminal amino acid sequence of this peptide was identical (except for a N/H substitution at position 2) to that deduced from a previously reported cDNA sequence (EMBL accession number X-13180), which had been misclassified as a Browman-Birk protease inhibitor. Pth-St1 did not inhibit either trypsin or insect alpha-amylase activities, and, in contrast with true thionins, did not affect cell-free protein synthesis or beta-glucuronidase activity. Northern-blot and tissue-print analyses showed that steady-state mRNA levels were highest in flowers (especially in petals), followed by tubers (especially in the epidermal cell layers and in leaf primordia), stems and leaves. Infection of leaves with a bacterial pathogen suspended in 10 mM MgCl2 switched off the gene, whereas mock inoculation with 10 mM MgCl2 alone induced higher mRNA levels.
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PMID:Pseudothionin-St1, a potato peptide active against potato pathogens. 803 86

Cadherins are Ca(2+)-dependent cell adhesion molecules that mediate cell adhesion by homophilic binding. Structural and functional analysis of the extracellular part of cadherins that mediates this binding has often been hampered by the availability of sufficient amount of protein. Therefore, we have expressed the extracellular region of E-cadherin (uvomorulin) using the baculovirus expression vector system (BEVS). A recombinant baculovirus was generated that encodes the signal peptide, the precursor region and the extracellular part of the mature protein, under the control of the promotor for polyhedrin. Infection of insect cells with recombinant virus led to the expression of about 40 mg of the E-cadherin fragment per 2 x 10(9) infected cells. About half of the protein synthesized was secreted, either as mature protein or in its unprocessed form. The precursor peptide was removed by trypsin treatment in the presence of Ca2+ and recombinant protein was purified to homogeneity. Biochemical characterization of the recombinant protein revealed a high degree of similarity with the mouse wild-type protein. Recombinant protein exhibited the known resistance to trypsin in the presence of Ca2+ and was recognized by two different conformation-sensitive monoclonal anti-E-cadherin antibodies. Rabbit antibodies made against the recombinant protein recognized E-cadherin from different species. In spite of the high degree of structural resemblance recombinant E-cadherin was not able to inhibit E-cadherin mediated cell-cell adhesion.
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PMID:Characterization of recombinant E-cadherin (uvomorulin) expressed in insect cells. 814 91


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