An enduring mystery for allergy researchers has been the unpredictable distribution of allergens in plants. For example, being allergic to birch pollen can predispose a person to allergy from distantly related plant foods such as celery, apple or soy.
Most allergens are proteins. Research published on Tuesday identifies 129 plant allergens in just four main protein families.
“Knowing what makes a protein more likely to become an allergen could make it easier for manufacturers to identify potential allergens in novel foods and ingredients, preventing them from reaching the consumer”, said Dr Clare Mills, head of the allergy research team at the UK’s Institute of Food Research.
Proteins are constructed from amino acids, and previous research has focused on analysing the sequence of amino acids to identify potential allergens. However, this can lead to false predictions. Sequence data alone does not reveal how amino acids interact to construct proteins.
The interaction of amino acids creates proteins folded into particular shapes. The new research by a team of scientists considered both amino acid sequence and structural similarities between surface features of plant proteins using a 3D computer model.
“By modelling surface features of proteins from a range of flowering plants, we were able to explain why cross-reactions can occur between species that otherwise seem dissimilar”, said Dr Mills. “This is especially important to help us understand why people with allergy to birch pollen can suffer related allergies to fresh fruits and vegetables”.
Flowering plants first appeared over 100 million years ago during the late Jurassic period, the age of the dinosaurs. Flowering plants became the most dominant plant on Earth and today include all our food plants. Very early in their evolution there was a split into two major groups. Some plant protein structures changed and some stayed the same or were ‘conserved’.
“We found that even a single conserved region on the surface structure of a protein can cause cross-reactivity”, said Dr Heimo Breiteneder of the Medical University of Vienna.