title: Identification of a novel hydroxyproline-rich glycoprotein as the major allergen in Parthenium pollen.
abstract: BACKGROUND
  The airborne pollen of the Compositae weed, Parthenium hysterophorus, is a major cause of allergic rhinitis in the Indian subcontinent and in certain parts of the southern United States and western Australia. Earlier studies have identified a 31 kd protein as the major allergen in Parthenium pollen.
  
  
  OBJECTIVE
  This study was undertaken to carry out the purification, immunochemical characterization, sequencing, and epitope analysis of this major allergen, designated as Par h I.
  
  
  METHODS
  The IgE-binding activity of the allergen was evaluated by immunoblot and inhibition ELISAs. Pronase digestion, periodate oxidation, and chemical deglycosylation were performed to determine the role of peptide and carbohydrate components of the allergen in IgE binding.
  
  
  RESULTS
  The data provide evidence for the involvement of carbohydrate moieties on Par h 1 in its IgE-binding ability. The N-terminal 91 amino acid sequence of Par h 1 shows 81% identity with a protein from sunflower anther, and the hydroxyproline-rich region of Par h 1 is 30% to 40% identical to similar stretches in extensins, a class of hydroxyproline-rich cell wall glycoproteins from different plant species. IgE antibodies in the sera of individuals allergic to Parthenium cross-reacted with a 50 kd hydroxyproline-arabinose-rich extensin precursor from potato tuber, and this binding was periodate-sensitive.
  
  
  CONCLUSIONS
  It appears that a group of soluble plant glycoproteins, which are related to the ubiquitous extensins, have certain carbohydrate-containing IgE-binding epitopes that may contribute to allergenic cross-reactivity among specific pollens and foods.
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore, India.
authors.forename: N
authors.initials: N
authors.lastname: Gupta
authors.forename: B M
authors.initials: BM
authors.lastname: Martin
authors.forename: D D
authors.initials: DD
authors.lastname: Metcalfe
authors.forename: P V
authors.initials: PV
authors.lastname: Rao
mesh_terms: D000485:Allergens / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D003429:Cross Reactions; D006023:Glycoproteins / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification*; D006031:Glycosylation; D006909:Hydroxyproline / Q000032:analysis*; D007073:Immunoglobulin E / Q000276:immunology; D037102:Lectins / Q000276:immunology; D008969:Molecular Sequence Data; D037121:Plant Lectins; D010940:Plant Proteins / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification*; D010944:Plants / Q000737:chemistry / Q000276:immunology*; D011058:Pollen / Q000737:chemistry / Q000276:immunology*; D011499:Protein Processing, Post-Translational; D017386:Sequence Homology, Amino Acid; D011198:Solanum tuberosum / Q000276:immunology
chemical_list: D000485:Allergens; D000596:Amino Acids; D006023:Glycoproteins; D037102:Lectins; C102723:Par h 1 allergen, Parthenium hysterophorus; D037121:Plant Lectins; D010940:Plant Proteins; D007073:Immunoglobulin E; D006909:Hydroxyproline