大豆ASR蛋白富含组氨酸结构域在结合金属离子中的作用

利用固相亲和层析实验结果表明,GmASR蛋白及其含组氨酸结构域A1~A5短肽可与金属离子Cu2+和Cd2+结合；采用Cu-抗坏血酸体系检测了GmASR蛋白及A1~A5清除羟基自由基的能力，证明GmASR蛋白及A1~A5短肽中组氨酸数目与清除羟基自由基能力呈正相关；GmASR蛋白及A1~A5可保护DNA分子免受Cu2+造成的氧化损伤.CD实验和SDS-PAGE实验结果发现，GmASR蛋白及A1~A5短肽与Cu2+结合后将引起可逆性聚集及沉淀.可见GmASR蛋白通过组氨酸结合过多的金属离子，维持细胞内离子平衡，是保护植物免受重金属毒害的重要机制之一.

The Role of Soybean ASR Protein Histidine-Rich Domain on Binding Metal Ions

In this paper, the Cu2+ and Cd2+ binding properties of GmASR protein and its truncated polypeptides A1~A5 containing histidine were detected using immobilized metal ion affinity chromatography (IMAC). Then, the hydroxyl radicals reducing activities of GmASR protein and the polypeptides A1~A5 were determined by Cu-ascorbate system and it was found that the hydroxyl radicals reducing activities of GmASR and the polypeptides A1~A5 have a positive correlation with the number of histidine residues in their sequences. In addition, GmASR protein and polypeptides A1~A5 could protect DNA from oxidative damage caused by Cu2+.The results of CD and SDS-PAGE experiments indicated that Cu2+ binding to GmASR protein would cause reversible aggregation and precipitation of the protein and polypeptides in vitro. We speculate that GmASR can bind excess metal ions in the cytoplasm by means of the histidine-rich motifs and maintain intracellular ion balance and protect plants from heavy metal toxicity.