title: Low-molecular-weight polypeptides of vicilin from Vicia faba L. are products of proteolytic breakdown.
abstract: Vicilin, the main 7-S globulin of Vicia faba L., undergoes cleavage during prolonged treatment at room temperature, which can be inhibited by protease inhibitors such as 1 microM leupeptin. The cleavage products show identical electrophoretic mobilities with the polypeptides normally visible after sodium dodecylsulphate gel electrophoresis of vicilin prepared from mature seeds. N-terminal amino acid analysis of electrophoretically prepared polypeptides reveals serine as common N terminus of the two largest polypeptides of Mr approximately equal to 50000 and 35000. According to serological experiments and peptide mapping the low-molecular-weight polypeptides (Mr approximately equal to 35000; 31000; 19000 and below) have antigenic determinants and amino acid sequences, respectively, that are similar to each other and are all contained within the structure of the large polypeptide of Mr approximately equal to 50000. This leads of the conclusion that polypeptides of Mr approximately equal to 35000 and below are derived by proteolysis from one (or a few closely related) polypeptide(s) of Mr approximately equal to 50000 and that proteolysis starts soon after biosynthesis as a post-translational process within the developing seed. Some experiments indicate the existence of 'nicking' points within the vicilin polypeptides, which are the major cleavage sites during preparation. These observations strongly support the view that 'native' vicilin is a trimeric or tetrameric globulin with polypeptides of Mr greater than or equal to 50000.
mesh_terms: D000595:Amino Acid Sequence; D055598:Chemical Phenomena; D002621:Chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D007887:Fabaceae / Q000032:analysis; D007122:Immunoelectrophoresis; D008970:Molecular Weight; D010446:Peptide Fragments / Q000302:isolation & purification*; D010447:Peptide Hydrolases / Q000502:physiology; D010940:Plant Proteins; D014674:Plant Proteins, Dietary / Q000032:analysis / Q000302:isolation & purification*; D010946:Plants, Medicinal; D055314:Seed Storage Proteins
chemical_list: D010446:Peptide Fragments; D010940:Plant Proteins; D014674:Plant Proteins, Dietary; D055314:Seed Storage Proteins; C015575:vicilin protein, plant; D010447:Peptide Hydrolases