2S methionine-rich protein (SSA) from sunflower seed is an IgE-binding protein

Background: Sunflower seed contains 2S albumins that in other crops have been associated with allergenicity. The sunflower seed methionine-rich 2S albumin (SSA) may be an IgE-binding protein responsible for anaphylactic reactions in some sunflower seed-sensitive subjects. The objective was to demonstrate that SSA is an IgE-binding protein. Methods: SSA was purified and the amino-acid sequence determined. The degree of purity of SSA was evaluated by silver staining, and its IgE-binding capacity by immunoblotting with serum from a subject with a convincing clinical history of anaphylaxis to sunflower seed. Results: The amino-acid sequence confirmed that the purified protein was the mature form of the methionine-rich storage protein SSA from sunflower seed (Helianthus annuus). The SSA was specifically recognized by IgE from the serum of the sunflower seed-allergic subject. Conclusions: SSA is an IgE-binding protein, and subjects allergic to sunflower seed whose IgE binds to SSA are at risk of developing allergic reactions if they consume SSA.