Structural analysis of globulins isolated from genetically different Amaranthus hybrid lines

The main storage protein of Amaranthus species, the oligomeric salt-soluble globulin was isolated and purified to homogeneity from six genetically different Amaranthus lines and compared with a previously investigated line i.e., Amaranthus K343. Physico-chemical analyses revealed that some heterogeneity existed with respect to the overall molecular weight of the globulins tested, as did differences in the molar ratio of their constituent (individual) subunits. Amino acid compositions of these proteins were found to be very similar and characteristically high in aspartic/asparagine and glutamic/glutamine amino acids. Circular dichroic studies revealed that all globulins shared similar secondary structural conformations characterized by low α-helical and high β-sheet contents. Although internal conformations were found to be very highly conserved, tertiary structural analysis revealed that substantial differences existed in the arrangement/proximity and exposure of aromatic amino acids on globulin surfaces.