The structure of the 12 S globulin from rapeseed (Brassica napus L.)

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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 (D3). 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.