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Allergenic relevance of nonspecific lipid transfer proteins 2: Identification and characterization of Api g 6 from celery tuber as representative of a novel IgE-binding protein family

Authors

  • Eva Vejvar,

    1. Christian Doppler Laboratory for Allergy Diagnosis and Therapy, Department of Molecular Biology, University of Salzburg, Salzburg, Austria
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  • Martin Himly,

    1. Christian Doppler Laboratory for Allergy Diagnosis and Therapy, Department of Molecular Biology, University of Salzburg, Salzburg, Austria
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  • Peter Briza,

    1. Christian Doppler Laboratory for Allergy Diagnosis and Therapy, Department of Molecular Biology, University of Salzburg, Salzburg, Austria
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  • Stephanie Eichhorn,

    1. Christian Doppler Laboratory for Allergy Diagnosis and Therapy, Department of Molecular Biology, University of Salzburg, Salzburg, Austria
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  • Christof Ebner,

    1. Allergy Clinic Reumannplatz, Vienna, Austria
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  • Wolfgang Hemmer,

    1. FAZ-Floridsdorf Allergy Center, Vienna, Austria
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  • Fatima Ferreira,

    1. Christian Doppler Laboratory for Allergy Diagnosis and Therapy, Department of Molecular Biology, University of Salzburg, Salzburg, Austria
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  • Gabriele Gadermaier

    Corresponding author
    1. Christian Doppler Laboratory for Allergy Diagnosis and Therapy, Department of Molecular Biology, University of Salzburg, Salzburg, Austria
    • Correspondence: Dr. Gabriele Gadermaier, Christian Doppler Laboratory for Allergy Diagnosis and Therapy, Department of Molecular Biology, University of Salzburg, Hellbrunnerstraße 34, A-5020 Salzburg, Austria

      E-mail: Gabriele.Gadermaier@sbg.ac.at

      Fax: +43-662-8044-183

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Abstract

Scope

Apium graveolens represents a relevant food allergen source linked with severe systemic reactions. We sought to identify an IgE-binding nonspecific lipid transfer protein (nsLTP) in celery tuber.

Methods and results

A low molecular weight protein exclusively present in celery tuber was purified and designated Api g 6. The entire protein sequence was obtained by MS and classified as member of the nsLTP2 family. Api g 6 is monomeric in solution with a molecular mass of 6936 Da. The alpha-helical disulfide bond-stabilized structure confers tremendous thermal stability (Tm > 90°C) and high resistance to gastrointestinal digestion. Endolysosomal degradation demonstrated low susceptibility and the presence of a dominant peptide cluster at the C-terminus. Thirty-eight percent of A. graveolens allergic patients demonstrated IgE reactivity to purified natural Api g 6 in ELISA and heat treatment did only partially reduce its allergenic activity. No correlation in IgE binding and limited cross-reactivity was observed with Api g 2 and Art v 3, nsLTP1 from celery stalks and mugwort pollen.

Conclusion

Api g 6, a novel nsLTP2 from celery tuber represents the first well-characterized allergen in this protein family. Despite similar structural and physicochemical features as nsLTP1, immunological properties of Api g 6 are distinct which warrants its inclusion in molecule-based diagnosis of A. graveolens allergy.

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