Characterization of Radish (Raphanus sativus) Storage Proteins

Radish (Raphanus sativus cv Rond rose à bout blanc Vilmorin) seeds, as other cruciferae oil seeds, contain two major types of storage protein aggregates which can be separated by gel filtration into 12 and 1.7 Svedberg fractions. These two fractions have been characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, amino acid composition, and two bidimensional gel electrophoresis systems. These results were compared with those obtained with rapeseed storage proteins. Radish 12 Svedberg particles are made of a series of nine major polypeptides ranging from 33 to 30 kilodaltons. These polypeptides present charge heterogeneity. The 12 Svedberg particle is made of six subunits approximately 55 kilodaltons. Each subunit is a couple of two polypeptides linked by a disulfide bridge. The 1.7 Svedberg particle has a simpler composition. It is made of two polypeptides of 10 and 12 kilodaltons and smaller peptides of approximately 7 kilodaltons. Twelve and 1.7 Svedberg particles also differ in their amino acid composition, the 1.7 Svedberg being particularly rich in glutamic acid and proline. Its components are basic. The organization of the rapeseed storage protein is similar but more complex.