ISOLATION, PURIFICATION AND CHARACTERIZATION OF THE SEED STORAGE GLOBULIN AND ITS POLYMERIZED FORM FROM TRITICUM-AESTIVUM

The salt-soluble globulin and its polymerized counterpart from wheat ( Triticum aestivum) seed were isolated and purified to homogeneity empl oying both gel filtration and anion exchange chromatography. The two g lobulins were purified free of any purothionin (an oxidation-reduction protein) contamination. Some of the physico-chemical properties of pu rothionin are also reported. Both globulins were found to be oligomers composed of two polypeptide chains, i.e., 35,000 and 49,000 Da, with no apparent evidence of any covalent inter-chain disulfide linkages be tween these major subunits. The molecular weights for the globulin and its polymerized (i.e., polymerized via interchain disulfide bonds bet ween various subunits of differing molecular weights, excluding any in terchain disulfide bonds between the 35,000 and 49,000 Da subunits) co unterpart were determined to be 474,000 and 567,000 Da, respectively, by gel chromatography. Surface charge profiles of fractions 2 and 3 we re determined using electrophoretic isoelectric focusing, electrophore tic titration and zeta potential analysis and indicated pIs of 6.90 an d 6.55, respectively. The nonpolymerized globulin was found to be more positively charged below its isoelectric point and less negatively ch arged above it than its polymerized counterpart. Microcalorimetric stu dies indicated that the two globulins had similar T-m values.