Birch pollen is a common allergen that plagues hay fever sufferers. People allergic to birch pollen often also develop allergic reactions to apples. The major allergen in apples is the protein Mal d 1. Patients can be sensitized to this apple protein by contact with the allergen Bet v 1 in birch pollen. Until now, there had been no experimentally verified structural data for Mal d 1.
Martin Tollinger and colleagues, University of Innsbruck, Austria, have studied the protein’s isoform Mal d 1.0101, which was cloned from Granny Smith apples. The team used NMR spectroscopy to solve the structure of the protein in solution. They found that Mal d 1.0101 consists of a seven-stranded β-sheet and three α-helices, which together form a cavity inside the protein. The cavity has a comparatively large volume of 2230 Å3 and a hydrophobic surface. These properties are similar to the birch allergen Bet v 1.
According to the researchers, the solved structure of Mal d 1.0101 could provide a basis for the detailed study of immunological cross-reactivity between birch and apple allergens.
- Structure of the Major Apple Allergen Mal d 1,
Linda Ahammer, Sarina Grutsch, Anna S. Kamenik, Klaus R. Liedl, Martin Tollinger,
J. Agric. Food Chem. 2017.