A PROPOSED MECHANISM FOR THE CRYOAGGREGATION OF THE SEED STORAGE GLOBULIN AND ITS POLYMERIZED FORM FROM TRITICUM-AESTIVUM

The purified salt-soluble globulin and its polymerized (i.e., polymeri zed via interchain disulfide bonds between various subunits of differi ng molecular weights, excluding any interchain disulfide bonds between the 35,000 and 49,000 Da subunits) counterpart from wheat (Triticum a estivum) seed were studied at a variety of temperatures and holding ti mes (i.e., 25, 15, 10C for holding times between 0 and 600 min). A mec hanism responsible for cryoaggregation is proposed. The polymerized fo rm of the globulin was found to be much more cryoaggregatable than the nonpolymerized form. Ultraviolet (UV) and circular dichroism (near- a nd far-UV) spectral analyses revealed that the polymerized globulin wa s more susceptible to conformational changes than its nonpolymerized f orm with decrease in temperature. It is suggested that the higher flex ibility of the polymerized globulin would allow for subtle changes in protein conformation, and therefore, permit the surface aromatic amino acids to interact with other hydrophobic groups on neighboring protei n molecules in a cooperative manner. The latter situation may result i n aggregation and precipitation.