Isolation and Partial Characterization of the Protein Body Membrane from Mature and Germinating Seeds of Vicia faba L.

Abstract

Summary Electron microscopical studies of Vicia faba seeds have been shown that the protein body envelope is a protein-lipid bilayer membrane with a mean diameter of about 100 A. Protein body membranes from Vicia faba seeds were separated from protein body contents by successive salt extractions after sonication of the isolated protein bodies. Purity of the remaining membrane fraction was checked by serological techniques. A protein content of about 20% was determined on a dry weight basis. Polyacrylamide gel electrophoresis in the presence of SDS revealed about 30 polypeptides with apparent molecular weights up to about 85,000 D. Among them were 15 polypeptides which showed a positive reaction after Schiff’s staining. After urea treatments of the membrane fraction differences in the gel electropherograms of urea extractable polypeptides compared with the urea treated material were observed. SDS-polyacrylamide gel electrophoresis of protein body membranes from germinating seeds revealed no detectable changes with respect to main polypeptides of the membrane fraction during the first 6 days of seed germination. Furthermore the presence of a membrane boundary was demonstrated by electron microscopical studies of protein bodies in the cotyledons from germinating seeds even after partial loss of contrasted material from the protein body contents.