Abstract:

Rice Cd-binding protein (RCBP) was obtained from high-Cd rice using alkali extraction, thermal denaturation
and ethanol precipitation. Physicochemical characteristics including UV absorbance, amino acid composition, molecular
weight and secondary structures were investigated. The results showed that all the alkali-extractable protein (AP), thermally
denaturated protein (TP) and ethanol-precipitated protein (EP) had the maximum absorption peak at 210 nm and similar
amino acid composition. The 94-kD protein was completely removed and the 5 094-kD protein was decreased by the thermal
denaturation. Moreover, the ethanol precipitation resulted in a further reduction of the 50-kD and 14-kD proteins. The major
secondary structures of AP were α-helical and β-turn, while β-sheet and β-turn were found in TP. On the other hand, β-sheet
and β-turn were predominant in EP. These results indicated that thermal denaturation and ethanol precipitation could be used
to separate RCBP from AP.

Key words: rice Cd-binding protein, thermal denaturation, ethanol precipitation, physicochemical characteristic