Tandem repeat inserts in 13S globulin subunits, the major allergenic storage protein of common buckwheat (Fagopyrum esculentum Moench) seeds

► β Polypeptides of 13S globulin subunits are prevalent allergen in common buckwheat. ► α Polypeptides, a counterpart of the β polypeptides, were minutely characterised. ► Four new methionine-poor subunits with 0, 2, 4, and 6 tandem repeats were identified. ► The insertion of the tandem repeats enlarged the diversity of the α polypeptides. ► The insertion also reduced the stability of the α polypeptides against trypsin.