Protein Profiles of Major Korean Rice Cultivars

The protein profiles among Korean rice cultivars were assessed by total protein determination, solubility fractionation, SDS-PAGE analysis and scanning densitometry. In the extraction of protein, the SDS/urea system at a neutral pH was more efficient than that at alkaline pH. The determination of total protein showed that the protein content was similar among cultivars, ranging from 87.9 to 92.7 ㎎/g dry weight. Additionally, the water/NaCl-soluble protein fraction, containing 14～16 kDa albumin and 22 kDa globulin α-globulin, was also similar among cultivars, with a range of 9.94 to 11.98 ㎎/g dry weight. The SDS-PAGE/densitometry of total protein showed that there was no discernable difference in proteins of higher molecular weights among various cultivars, whereas the amount of lower molecular weight proteins (14～16 kDa) is somewhat variable among cultivars. Furthermore, SDS-PAGE analysis of water/NaCl-soluble and propanol-soluble fractions indicates that there is a discernible change in the content of albumin, globulin or prolamin among cultivars. Thus, the PAGE/densitometry method, preceded by solubility fractionation, is useful for examining differences in protein profiles of rice cultivars.