Molecular heterogeneity and genetics of Vicia faba seed storage proteins

Legumin and vicilin were purified from seeds of Vicia faba L. var. Scuro, characterized in different electrophoretic systems, and used to produce polyclonal antibodies in rabbits. Two-dimensional electrophoretic studies showed a wide range of heterogeneity in the subunits of both legumin and vicilin. Legumin was found to be composed of 29 disulphide-linked subunit pairs with different molecular weight and/or isoelectric point. Western blot analysis of legumin of several mutants revealed molecular polymorphism based on a corresponding gene family. Three different α-major legumin patterns were found, and inheritance studies showed that the 34.3-kD legumin polypeptide is the product of one locus, Lg-1α, which is the first legumin genetic locus described in Vicia faba. Vicilin was found to be composed of as many as 59 subunits distributed in a molecular weight range of 65.7 to 42.8 kD (major polypeptides) and 37.2 to 15.2 kD (minor polypeptides), with different isoelectric points. A model is proposed that explains the possible formation of the minor subunits and the major subunits of 48.2 and 46 kD molecular weight (MW) from proteolytic cleavages and/or glycosilation of precursor polypeptides. Ten different vicilin electrophoretic patterns were observed among the analyzed accessions, which showed large molecular polymorphism that proved to be under genetic control.