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)

The action of trypsin and pronase on the haemagglutinins and neuraminidases of eight strains of influenza virus has been examined.The haemagglutinins of all the strains were highly susceptible to digestion by pronase but there were great variations in resistance to trypsin.The neuraminidases of the eight strains were of three types. The neuraminidases of the A 1 strains and the DSP strain of virus A were highly susceptible to destruction by both enzymes. The neuraminidases of the PR 8 and Swine strains showed partial resistance especially to trypsin, while the A 2 strains and the LEE strains of virus B possessed neuraminidases that were completely resistant to both trypsin and pronase.Proteolytic enzymes released free neuraminidases from the A 2 and LEE viruses the morphology of which was different from that of neuraminidases released by detergent treatment.
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PMID:The chemical reactions of the haemagglutinins and neuraminidases of different strains of influenza viruses. 3. Effects of proteolytic enzymes. 528 45

An assay is presented that allows continuous and sensitive monitoring of membrane fusion in both artificial and biological membrane systems. The method relies upon the relief of fluorescence self-quenching of octadecyl Rhodamine B chloride. When the probe is incorporated into a lipid bilayer at concentrations up to 9 mol% with respect to total lipid, the efficiency of self-quenching is proportional to its surface density. Upon fusion between membranes labeled with the probe and nonlabeled membranes, the decrease in surface density of the fluorophore results in a concomitant, proportional increase in fluorescence intensity, allowing kinetic and quantitative measurements of the fusion process. The kinetics of fusion between phospholipid vesicles monitored with this assay were found to be the same as those determined with a fusion assay based on resonance energy transfer [Struck, D. K., Hoekstra, D., & Pagano, R. E. (1981) Biochemistry 20, 4093-4099]. Octadecyl Rhodamine B chloride can be readily inserted into native biological membranes by addition of an ethanolic solution of the probe. Evidence is presented showing that the dilution of the fluorophore, occurring when octadecyl Rhodamine containing influenza virus is mixed with phospholipid vesicles at pH 5.0, but not pH 7.4, resulted from virus-vesicle fusion and was not related to processes other than fusion. Furthermore, by use of this method, the kinetics of fusion between Sendai virus and erythrocyte ghosts and virus-induced fusion of ghosts were readily revealed. Dilution of the probe was not observed upon prior treatment of fluorescently labeled Sendai virus with trypsin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Fluorescence method for measuring the kinetics of fusion between biological membranes. 609 95

The proteolytic susceptibility of polypeptides of four antigenically distinct subtypes of influenza a virus strains of human origin was studied. The extent of degradation of polypeptide molecules of strains A/PR/8/34 (H0N1) (PR), A/FM/1/47 (H1N1), A/Singapore/1/57 (H2N2) and A/Hong Kong/8/68 (H3N2), assessed by densitometry of gels after sodium dodecylsulfate polyacrylamide gel electrophoresis was variable by treatment with trypsin. Also, sequential treatment of PR strain initially with phospholipase D followed by proteases of different specificities suggested differences in susceptibility of surface and internal polypeptide molecules. The significance of these results is discussed.
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PMID:Protease susceptibility of human A influenza virus polypeptides. 611 61

The cold-adapted temperature-sensitive (ts) influenza virus strain A/Leningrad/134/17/57 (H2N2) multiplied well at 32 degrees C (optimal temperature); lower titres of infectious virus were obtained in developing chick embryos at 40 degrees C. In a canine kidney (MDCK) cell line and in primary calf kidney (CK) cells an increased reproduction of the virus was found at 40 degrees C especially in the presence of trypsin. The ratios of virus titres obtained at optimal versus higher temperatures (RCT40) were by 1,000 times lower than those found in chick embryos. Polyacrylamide gel electrophoresis revealed a comparable synthesis of the cold-adapted influenza virus strain polypeptides HA, NP, M and NS in MDCK cells, regardless whether they were incubated at optimal or non-permissive temperatures.
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PMID:Partial change of the ts-phenotype of cold-adapted influenza virus strain grown in canine kidney cells in the presence of trypsin. 612 30

The levels of neutral protease activity associated with allantoic and amniotic fluids of embryonated eggs during the replication of influenza strains A/PR/8/34 (H1N1) and A/turkey/Ontario/7732/66 (H5N9) were investigated. A sensitive fluorometric technique proved useful for characterization and monitoring changes of protease activities in egg fluids. The predominant type of protease in allantoic and amniotic fluids had trypsin-like specificities. Variation in protease levels of both fluids occurred throughout the course of virus replication irrespective of the virus strain or the route of inoculation used. Concomitant with the production of high levels of infectious virus there was a marked decrease in neutral protease activity in the fluid from the cavity initially infected. Translocation of virus also occurred especially with amniotically infected eggs, as evidenced by high infectious virus titers and decreased protease activities in allantoic fluids.
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PMID:Effects of influenza virus replication on neutral proteolytic activities in embryonated egg fluids. 613 79

Human influenza virus A/Krasnodar/101/59 (H2N2) was passaged in chick fibroblast cultures in the presence of trypsin at suboptimal temperature. The virus which underwent 16 passages at 28 degrees C possessed cold-adapted (ca) and temperature sensitive (ts) phenotypes and formed larger plaques at the optimal temperature (33 degrees C). Its reproduction in the lungs of hamsters was decreased as evidenced by approximately 2.5 log10 lower titres; only one of 9 virus isolates from the lungs of hamsters acquired the ts +/- phenotype, although it had retained a ca phenotype. Recombination of this variant with ts mutants of fowl plague virus (FPV) revealed a ts mutation only in gene 4 of this variant coding for haemagglutinin (HA). The virus which had had 25 passages at 28 degrees C possessed the same properties as the previous variant, but all eight virus isolates from the lungs of hamsters retained the ts phenotype; the genome of this variant contained ts mutations in genes 1, 3, 4, 5 and 6. The mutation found in gene 8 was not a ts mutation. The virus, which underwent 25 passages at 28 degrees C and additional 15 passages at 27 degrees C, formed large plaques and alike to the previous variants it possessed the ca and ts phenotypes; however, its reproduction in the lungs of hamsters was decreased by 4.0 log10 and occurred in the lungs only of 4 out 16 infected animals. This variant contained ts mutations in genes 1, 3, 4, 5, 6 and 7 and a non-ts mutation in gene 8.
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PMID:Ts mutations in the genome of cold-adapted variants of human influenza virus A/Krasnodar/101/59 (H2N2) at different passage levels and their reproduction in lungs of hamsters. 615 50

Six influenza B virus strains and one recombinant vaccine strain have been compared in cell cultures, hamsters and in hamster tracheal organ cultures. In cell cultures all strains plaque well with or without trypsin. All strains are restricted in growth above 38 degrees C. The cold adapted attenuated virus, influenza B/AA/1/66, and a cold recombinant, RB77, are also restricted in growth above 37 degrees C and thus have a temperature marker. In hamsters influenza B viruses, except strain B/Lee, grow well in lungs and nasal tissues. Small differences were seen between wild type viruses and the cold adapted irus and its recombinants which may serve as additional markers for attenuation.
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PMID:Studies with some influenza B viruses in cell cultures, hamsters and hamster tracheal organ cultures. 616 42

Encephalomyocarditis (EMC) virus causes lethal infection of hamsters against which poly(I) . poly(C) causes dose-dependent protection. In contrast, no antiviral effects occur with poly(I) . poly(C) against influenza virus infection of hamsters. Serum from poly(I) . poly(C) treated hamsters protects other hamsters against EMC virus infection with maximum protection with serum removed 3h after poly(I) . poly(C) treatment of the donor hamsters. In such assays the factor was found to be inactivated by trypsin and pH 2 and 56 degrees C for 1 hr. The serum factor did not confer protection against EMC virus infection of L-929, BHK, Hak or primary hamster embryo cells. The amount of poly(I) . poly(C) carried over into serum samples of poly(I) . poly(C) treated hamsters was insufficient to account for the antiviral effects. The antiviral serum factor is presumed to be a form of interferon despite the fact that it does not titrate in cell cultures and has a novel set of properties from those which describe known interferons.
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PMID:A putative interferon induced in hamsters by poly(I) . poly(C). 618 78

Exposure of influenza virus to an acidic environment, which is known to be required for viral fusion and hemolysis, has recently been shown to induce a conformational change in the hemagglutinin molecule. In the present study, we examined the effects of acid incubation on the antigenicity, biological activity, and morphology of influenza virus A/PR/8/34 (H1N1). Incubation of PR8 virus at pH 5 in the absence of erythrocytes resulted in a rapid and irreversible loss of viral hemolytic activity and infectivity. Apart from a less distinct appearance of the viral surface projections and slight damage to the envelope structure, acid incubation did not result in gross morphological changes in the viral architecture. The acid-induced change could be detected in the form of greatly increased or decreased binding of many monoclonal antibodies directed to each of the four major antigenic regions of the hemagglutinin. Triggering of viral hemolytic activity and antigenic alterations was similarly pH dependent. In addition, the different pH dependencies of egg-grown and trypsin-treated MDCK-grown viruses coincided with an analogous pH dependence of the antigenic alterations that were observed with these viruses. These observations are compatible with the idea that some of the anti-hemagglutinin antibodies detect conformational changes in the hemagglutinin which are required for the initiation of fusion and hemolysis.
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PMID:Monoclonal anti-hemagglutinin antibodies detect irreversible antigenic alterations that coincide with the acid activation of influenza virus A/PR/834-mediated hemolysis. 619 86

The present report attempts to determine if there are distinct epitopes on the T8 molecule that are involved in class I-restricted cytotoxic T lymphocyte (CTL) function. A panel of 9 monoclonal antibodies (OKT8A,B,C,E,F,G,H,I, and OKT5) was produced and all antibodies were shown to bind to the T8 molecule. This panel of antibodies was employed to characterize the distribution of distinct epitopes on the T8 molecule and to block the activity of class I-specific influenza virus-immune and allo-immune CTL effector function. Significant differences in the ability of the anti-T8 antibodies to block CTL function were observed: OKT8C and T8F blocked best (49 and 55% respectively); OKT8A,E,G,H,I, and OKT5 blocked less well (24-31%); and OKT8B blocked marginally (11%). There was no correlation between the capacity of the antibodies to block CTL function and their heavy chain isotype. Competitive binding of the different OKT8 antibodies to the cell surface and differential trypsin sensitivity of the epitopes recognized by the antibodies indicated that OKT8C and T8F were located on topographically distinct regions of the T8 molecule. These results indicate that specific epitopes on the T8 molecule are involved in CTL function, and that there could be more than one functional site on the molecule.
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PMID:Distinct epitopes on the T8 molecule are differentially involved in cytotoxic T cell function. 619 34


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