title: 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.
abstract: METHODS
  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.
  
  
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Christian Doppler Laboratory for Allergy Diagnosis and Therapy, Department of Molecular Biology, University of Salzburg, Salzburg, Austria.
authors.forename: Eva
authors.initials: E
authors.lastname: Vejvar
authors.forename: Martin
authors.initials: M
authors.lastname: Himly
authors.forename: Peter
authors.initials: P
authors.lastname: Briza
authors.forename: Stephanie
authors.initials: S
authors.lastname: Eichhorn
authors.forename: Christof
authors.initials: C
authors.lastname: Ebner
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hemmer
authors.forename: Fatima
authors.initials: F
authors.lastname: Ferreira
authors.forename: Gabriele
authors.initials: G
authors.lastname: Gadermaier
mesh_terms: D000485:Allergens / Q000032:analysis* / Q000276:immunology; D052179:Antigens, Plant / Q000032:analysis / Q000276:immunology; D000077102:Apium / Q000737:chemistry* / Q000276:immunology*; D002352:Carrier Proteins / Q000032:analysis / Q000276:immunology*; D002942:Circular Dichroism; D003429:Cross Reactions; D005512:Food Hypersensitivity / Q000175:diagnosis / Q000276:immunology; D037502:Galectin 3 / Q000032:analysis / Q000276:immunology*; D041981:Gastrointestinal Tract / Q000378:metabolism; D006801:Humans; D008970:Molecular Weight; D010940:Plant Proteins / Q000032:analysis* / Q000276:immunology; D059748:Proteolysis
chemical_list: D000485:Allergens; D052179:Antigens, Plant; D002352:Carrier Proteins; D037502:Galectin 3; D010940:Plant Proteins; C072087:sterol carrier proteins
keywords: Apium graveolens; Celery tuber; IgE reactivity; Nonspecific lipid transfer protein 2; Plant food allergy