Post-translational modifications influence IgE reactivity to the major allergen Phl p 1 of timothy grass pollen

Clin Exp Allergy. 1998 Mar;28(3):315-21. doi: 10.1046/j.1365-2222.1998.00221.x.


Background: Grass group I consists of very potent allergenic components which are found in the pollen of all temperate grasses. Several post-translational modifications are predicted from the cDNA data.

Objective: The aim of this study was to identify sequential IgE-binding sites on the allergen Phl p 1 and to determine their influence on IgE reactivity.

Methods: Based on cDNA data and microsequencing results we synthesized overlapping decapeptides covering the complete Phl p 1 molecule and tested them for immunological reactivity by means of the PEPSCAN technique. In a dot test we determined the frequency of IgE reactivities to post-translationally modified structures (hydroxylated proline residues, carbohydrate structure, and disulphide formations).

Results: Screening by overlapping peptides demonstrated an IgE binding site on the 10 N-terminal amino acids. Comprehensive studies showed that the two hydroxyproline residues of the native Phl p 1 allergen (at positions 5 and 8) and the N-glycan (at position 9) can result in an increased IgE reactivity; 3.3% of the sera exclusively bound to the hydroxyproline bearing peptide, while only 0.4% bound to the proline containing peptide. With regard to glycosylation, we estimated that 20% of sera recognized protein and carbohydrate epitopes, while one serum exclusively bound to the glycan. The formation of disulphide bonds has no detectable effect on the IgE reactivity to Phl p 1.

Conclusion: Our results indicate that the post-translational modifications, the carbohydrate structure and the hydroxylation of proline residues, can enhance the IgE reactivity of Phl p 1.

MeSH terms

  • Allergens*
  • Antigen-Antibody Reactions
  • Disulfides / immunology
  • Enzyme-Linked Immunosorbent Assay
  • Epitope Mapping
  • Glycosylation
  • Humans
  • Hydroxyproline / immunology
  • Immunoblotting
  • Immunoglobulin E / immunology*
  • Plant Proteins / chemistry
  • Plant Proteins / immunology*
  • Plant Proteins / metabolism
  • Protein Processing, Post-Translational*


  • Allergens
  • Disulfides
  • Plant Proteins
  • PHLPI protein, Phleum pratense
  • Immunoglobulin E
  • Hydroxyproline