STUDY OF THE CHARGE PROFILE AND COVALENT SUBUNIT ASSOCIATION OF THE OLIGOMERIC SEED GLOBULIN FROM AMARANTHUS-HYPOCHONDRIACUS

The physicochemical properties of the oligomeric salt-soluble seed globulin from Amaranthus hypochondriacus were examined in relationship to its surface charge and subunit association. The globulin was found to undergo substantial change in surface charge density as a function of pH. Aliphatic hydrophobicity was greatest in the pH range 4.5-6.8 and was attributed to changes in tertiary structure resulting in exposure of interior aliphatic amino acids. The pI of the globulin was determined to be 4.80, which corresponded to the point of highest aliphatic surface hydrophobicity. The globulin was composed of specific subunits linked through disulfide bridges to form dimers. Two distinct sedimenting populations indicating the occurrence of different hybrids or differing polymorphic forms of the globulin were observed.