Structural Characterization of the Allergenic 2S Albumin Cor a 14: Comparing Proteoform Patterns across Hazelnut Cultivars

The
hazelnut allergen Cor a 14 belongs to the 2S albumins, a family
of heterodimeric seed storage proteins exhibiting a high degree of
structural diversity. Given its relevance as an allergen and the potential
to elicit severe reactions, elucidation of the sequence heterogeneity
of naturally occurring Cor a 14 is essential for the development of
reliable diagnostics and risk evaluation. We therefore performed a
comprehensive survey on the proteoforms of Cor a 14 and determined
their quantitative distribution in three different hazelnut cultivars
by a combinatory HPLC–HRMS approach including bottom-up and
intact mass analysis. Compared with the Cor a 14 prototype sequence,
we identified three sequence polymorphisms, two of the small and one
of the large subunit, and elucidated their specific pairing on the
protein level. Furthermore, we located a pronounced microheterogeneity
on the protein termini and, for the first time, provide data on varying
proteoform patterns between different cultivars of an allergenic seed.
Together, these data present the basis for a more detailed investigation
on the allergenicity of Cor a 14 in different cultivars and constitute,
to be best of our knowledge, the largest set of proteoforms so far
reported for a 2S albumin.