Three dimensional Structure of Glycinin, a 11S Globulin from Peanut (Arachis hypogaea)

Department of Crystallography and Biophysics, University of Madras
â—‹Saraboji Kadhirvel Balasundaresan Dhakshnamoorthy Ponnuswamy Mondikalipudur Nanjappagounder

Seed storage proteins of grain crops meet the major dietary protein requirement of over half of the world population and play a major nitrogen source for the developing plant. Most of the plant seeds contain 11S globulins as major storage proteins for their nutrition. Large quantities of storage proteins are accumulated in developing seeds of leguminous plants that function as a reserve of carbon and nitrogen used during germination and early growth. A Glycinin, 11S globulin, is one of the major storage proteins in peanut and accounts for about 50% of the total seed proteins. Thus, glycinin plays an important role in the properties of food made from peanut. The protein glycinin was purified from the globulin fraction of peanut seed and the crystal structure was determined at 3.5Å resolution. The crystals grown under 30%MPD are rhombohedral with space group R3. The overall fold of the present model is consistent with the storage protein structures and this fold comes under the cupin superfamily domain. The crystal structure shows that the hexamer has 32-point group symmetry formed by face-to-face stacking of two trimers and these trimmers are stabilized by hydrophobic, electrostatic and hydrogen bonding interactions. The inter and intra-chain disulphide bonds conserved in the 11S globulin family are clearly observed.