The structure of the 12 S globulin from rapeseed (<i>Brassica napus L.</i>)

Abstract

Abstract The 12 S globulin of rapeseed represents an oligomeric protein with a molecular weight of 300,000. It is composed of 6 subunits, which are arranged in a trigonal antiprism with the point group symmetry 32 (D 3 ). Each subunit contains smaller units (polypeptide chains) with molecular weights in the range of 18,500 to 31,000. The protein contains the following 4 polypeptide chains differing by their molecular weights in the SDS‐electrophoresis; 18,500 ± 800, 21,100 ± 500, 26,800 ± 900, 31,200 ± 1,600. According to its quaternary structure the protein dissociates under milieu conditions. The secondary structure of the protein is characterized by a low (11 %) content of α‐helix and a relatively high (31%) content of β‐conformation. Owing to its structure and physico‐chemical properties the rapeseed protein is closely related to other 11/12 S globulins in the seeds of different plant species and botanical families.