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  • 1
    Electronic Resource
    Electronic Resource
    Role of residues constituting the 2β1 strand of domain II in the biological activity of anthrax protective antigen (2001)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 199 (2001), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Anthrax toxin consists of three proteins, protective antigen, lethal factor and oedema factor. A proteolytically activated 63-kDa fragment of protective antigen binds lethal factor/oedema factor and translocates them into the cytosol. Domain II of protective antigen has been implicated in membrane insertion and channel formation. In the present study, alanine substitutions in 14 consecutive residues of the 2β1 strand that are highly homologous to the putative membrane interacting segment of Clostridium perfringens iota-b toxin were generated and the effect on the biological activity of protective antigen studied. One of the mutants, Pro260Ala, showed considerably reduced toxicity in combination with lethal factor. The mutant also showed decreased membrane insertion and translocation of lethal factor into the cytosol. The data suggest that Pro260 is important for membrane insertion and translocation by protective antigen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2001.tb10646.x
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  • 2
    Electronic Resource
    Electronic Resource
    Epi p 1, an allergenic glycoprotein of Epicoccum purpurascens is a serine protease (2004)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 42 (2004), S. 0 
    Details
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Epicoccum purpurascens (EP) is a ubiquitous saprophytic mould, the inhalant spores and mycelia of which are responsible for respiratory allergic disorders in 5–7% of population worldwide. The diagnosis/therapy of these disorders caused by fungi involves the use of standardized and purified fungal extracts. A 33.5 kDa glycoprotein, Epi p 1 released histamine from whole blood cells of EP allergic patients at a concentration of 50-ng protein. The high specific IgE values detected in EP hypersensitive sera indicated that Epi p 1 is capable of mediating type I hypersensitive reaction in predisposed individuals. It also showed protease activity by virtue of its dose dependent cleavage of serine protease specific synthetic substrate, N-benzoyl arginine ethyl ester hydrochloride (BAEE). The serine protease nature of Epi p 1 was confirmed by its N-terminal sequence (ADG/FIVAVELD/STY) homology to a subtilisin like serine protease. The protease activity of Epi p 1 may be responsible for making its way into the system of pre-disposed individuals through epithelial cell detachment and the histamine releasing ability by cross-linking of IgE antibodies on cell surface is the cause of its allergenic nature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsim.2004.05.003
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  • 3
    Electronic Resource
    Electronic Resource
    Anthrax toxin lethal factor contains a zinc metalloprotease consensus sequence which is required for lethal toxin activity (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 13 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Comparison of the anthrax toxin lethal factor (LF) amino acid sequence with sequences in the Swiss protein database revealed short regions of similarity with the consensus zinc-binding site, HEXXH, that is characteristic of metalloproteases. Several protease inhibitors, including bestatin and captopril, prevented intoxication of macrophages by lethal toxin. LF was fully inactivated by site-directed mutagenesis that substituted Ala for either of the residues (H-686 and H-690) implicated in zinc binding. Similarly, LF was inactivated by substitution of Cys for E-687, which is thought to be an essential part of the catalytic site. In contrast, replacement of E-720 and E-721 with Ala had no effect on LF activity. LF bound 65Zn both in solution and on protein blots. The 65Zn binding was reduced for several of the LF mutants. These data suggest that anthrax toxin LF is a zinc metallopeptidase, the catalytic function of which is responsible for the lethal activity observed in cultured cells and in animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb00500.x
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  • 4
    Electronic Resource
    Electronic Resource
    Immunomodulation by liposome entrapped allergen (1990)
    Springer
    Molecular and cellular biochemistry 97 (1990), S. 173-179 
    Details
    ISSN: 1573-4919
    Keywords: liposome ; allergen ; immunomodulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Liposomes are non-toxic, biodegradable and feebly immunogenic lipid vesicles made from natural and synthetic lipids. They are known to act as immunopotentiating agents and can be used to formulate sustained release preparation by encapsulation. In the present study, liposome entrapped allergen and free allergen were used to inject in Balb/C mice at different time intervals and their immune response in terms of specific IgG and specific IgE levels was quantitated by ELISA (Enzyme Linked Immuno sorbent Assay). The results indicated that specific IgE response was significantly higher in mice injected free allergen as compared to that of mice given liposome entrapped allergen. However, the specific IgG response was not statistically significant. Experiments carried out with liposome entrapped allergen and liposome coupled allergen showed no statistically significant difference in specific IgE and specific IgG titre between the two groups of mice. This type of immunomodulatory effect of liposomes in reducing IgE levels and without affecting IgG levels may be useful in Type I allergic disorders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221059
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  • 5
    Electronic Resource
    Electronic Resource
    Ribonuclease activity dependent cytotoxicity of Asp fl, a major allergen of A. fumigatus (1997)
    Springer
    Molecular and cellular biochemistry 175 (1997), S. 21-27 
    Details
    ISSN: 1573-4919
    Keywords: Aspergillus fumigatus ; ribonuclease ; cytotoxicity ; Asp fl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A major allergen/antigen, Asp fl, secreted by Aspergillus fumigatus exhibits cytotoxicity towards eukaryotic cell lines. Asp fl inhibited protein synthesis in RAW cells with an IC50 of 4.5 nM and also degraded ribosomal RNA of RAW cells at a similar concentration. Ribosomal inactivation by Asp fl may be the probable mechanism for protein synthesis inhibition. Specifc ribonuclease activity of Asp fl was observed to be 100,000 U/mg. Presence of strong RNase activity in Asp fl was further confirmed by agar gels containing yeast RNA. Electrophoretic run on agarose gels showed that Asp fl degrades all species of naked RNA. Modification of histidine residues of Asp fl with diethyl pyrocarbonate and alkylation of cysteines with iodoacetamide resulted in loss of ribonuclease activity and cytotoxicity of Asp fl. The current study establishes the ribonuclease activity of a purified major allergen of A. fumigatus that inhibits protein synthesis and kills the eukaryotic cells. (Mol Cell Biochem 175: 21–27, 1997)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006822906343
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  • 6
    Electronic Resource
    Electronic Resource
    Identification and evaluation of a major cytotoxin of A. fumigatus (1997)
    Springer
    Molecular and cellular biochemistry 167 (1997), S. 89-97 
    Details
    ISSN: 1573-4919
    Keywords: Aspergillus fumigatus ; Asp fl ; major allergen ; cytotoxicity ; eukaryotic cell lines ; internalisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Aspergillus fumigatus is a highly pathogenic fungus causing a wide spectrum of diseases in immunocompromised as well as immunocompetent hosts. The present work was undertaken to evaluate the cytotoxic nature of fractionated antigens of A. fumigatus against the mammalian cell lines (J774, RAW, CHO and L929). An enriched protein antigenic fraction of A. fumigatus was subjected to con A Sepharose and phenyl Sepharose chromatography. Antigenic fractions, ConAub (conA unbound) and PSC III (fraction III of phenyl Sepharose column) containing low mw antigens showed higher cytotoxicity as compared to other antigenic fractions. PSC III was further purified on HPLC resulting in an 18 kDa homogeneous protein. The purified protein showed high ELISA absorbance values for specific IgG and IgE antibodies in sera of ABPA patients. Monoclonal antibody raised against Asp fl, a major allergen/antigen of A. fumigatus recognised the purified 18 kDa by ELISA and western blot. The 18 kDa allergen/antigen or Asp fl showed similar toxicity towards all the four cell lines (macrophage and fibroblast) with an IC50 of 75 ng/ml or 4.16 nM. Reduction in toxicity of 18 kDa at low temperatures and potentiation in presence of ammonium chloride and monensin indicates mechanism of internalisation of 18 kDa in eukaryotic cells is similar to α-sarcin. The present work shows that the 18 kDa allergen/antigen (Asp fl) is a major cytotoxin secreted by A. fumigatus which may play multiple roles in the pathogenesis of Aspergillosis through allergenicity, antigenicity and cytotoxicity. (Mol Cell Biochem 167: 89-97, 1997)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006823706119
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  • 7
    Electronic Resource
    Electronic Resource
    Site directed mutagenesis of Histidine residues in Anthrax toxin lethal factor binding domain reduces toxicity (1997)
    Springer
    Molecular and cellular biochemistry 177 (1997), S. 7-14 
    Details
    ISSN: 1573-4919
    Keywords: Anthrax ; recombinant ; mutagenesis ; lethal factor ; binding domain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Anthrax lethal toxin is a mixture of protective antigen (PA, 735 AA) and lethal factor (LF, 776 AA). Earlier studies have shown that 254 residues of lethal factor are sufficient for PA binding to cause internalization (Arora N and Leppla SH, J Biol Chem 268: 3334-3342, 1993). The present study was undertaken to determine residues which are important for binding of LF to PA. LF modification with diethyl pyrocarbonate (DEPC, modifies histidine residue primarily) results in the loss of binding and toxicity in mammalian cells. There are nine histidine residues in the binding domain. To locate the important residue(s), site-directed mutagenesis of these histidines were performed by recombinant methods. Replacement of His42 with Gly42 destablizes the protein and hence it could not be purified. His35 when mutagenized to Gly35 (mLF-DTA) diminishes the toxicity by 20 fold. Time dependent studies show that binding of mLF-DTA was reduced at shorter incubations and longer incubations taper off this difference. Gel shift assay suggested 8-10% less binding of mLF-DTA as compared to LF-DTA. In conclusion His35 is important for binding and His42 is critical and confers proper conformation for LF binding to PA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006815306876
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