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Cockroach allergen Bla g 2: an unusual aspartic proteinase

Journal of Allergy and Clinical Immunology, 2005-07, Vol.116 (1), p.140-145 [Peer Reviewed Journal]

ISSN: 0091-6749 ;EISSN: 1097-6825 ;EISSN: 1365-2567 ;DOI: 10.1016/j.jaci.2005.04.024 ;PMID: 15990787

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  • Title:
    Cockroach allergen Bla g 2: an unusual aspartic proteinase
  • Author: Wünschmann, Sabina ; Gustchina, Alla ; Chapman, Martin D ; Pomés, Anna
  • Subjects: Amino Acid Sequence ; Animals ; Aspartic Acid Endopeptidases - genetics ; Aspartic Acid Endopeptidases - immunology ; Aspartic Acid Endopeptidases - metabolism ; Cockroaches - immunology ; Enzyme Activation - immunology ; Molecular Sequence Data ; Mutagenesis, Site-Directed ; Pepstatins - metabolism ; Recombinant Proteins - genetics ; Recombinant Proteins - immunology ; Recombinant Proteins - metabolism
  • Is Part Of: Journal of Allergy and Clinical Immunology, 2005-07, Vol.116 (1), p.140-145
  • Description: Enzymatic activity of mite, fungal, and bee venom allergens is thought to potentiate their allergenicity. Bla g 2 is a potent cockroach allergen, but despite sharing sequence homology with aspartic proteinases, it contains critical amino acid substitutions that impair proteolytic activity. The biologic function of Bla g 2 remains unclear. We sought to investigate the effects of specific amino acid substitutions on enzymatic activity, and the peptide-binding capability of Bla g 2. Site-directed mutagenesis was used to produce a recombinant Bla g 2 mutant (Mut) with corrected canonical triads and a flap region. Another mutant (MutF - ) was expressed after additional mutations in the flap region of Mut. Bla g 2 wild-type (Wt), Mut, and MutF - were assayed for aspartic proteinase activity, and Bla g 2 Wt was tested for pepstatin binding. Recombinant Bla g 2 Wt and Mut did not show enzymatic activity in a milk-clotting and hemoglobin assay. By using a modified hemoglobin assay, residual activity inhibited by pepstatin was detected for MutF - and Wt at 20 microg/mL, whereas pepsin was active at a 1000-fold lower concentration. Most of Bla g 2 binding to pepstatin-agarose was nonspecific. Residual proteolytic activity was found for Bla g 2 at concentrations of approximately 4 mM. This weak activity suggests that proteolysis is not the primary function of this allergen and that it is unlikely to contribute to the allergenicity of Bla g 2. Bla g 2 has a cleft that might specifically bind ligands other than pepstatin.
  • Publisher: United States
  • Language: English
  • Identifier: ISSN: 0091-6749
    EISSN: 1097-6825
    EISSN: 1365-2567
    DOI: 10.1016/j.jaci.2005.04.024
    PMID: 15990787
  • Source: IngentaConnect Free/Open Access Journals
    GFMER Free Medical Journals
    MEDLINE
    PubMed Central
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