摘要
以玉米根微粒体为材料进行的微量放射配体结合（ＭＲＬＢ）实验表明玉米根微粒体膜上存在着ＡＢＡ结合位点，ＡＢＡ与ＡＢＡ结合蛋白（ＡＢＡ－ＢＰ）结合的最适ｐＨ为６．５，结合反应对温度（０℃和２５℃）不太敏感，ＡＢＡ与ＡＢＡ－ＢＰ的结合反应是一个动态平衡过程，５ｍｉｎ即可达最大结合（Ｂｍａｘ）的５０％，３０ｍｉｎ达到最大结合，１ｈ内基本保持不变。胰蛋白酶处理表明此结合位点为蛋白质，冻融实验则表明此蛋白与ＡＢＡ的结合不仅要求其自身具有特定构象而且需要有一定的膜脂环境，ＤＴＴ处理实验结果显示ＡＢＡ－ＢＰ中可能存在着二硫键。逆境处理可以提高玉米根微粒体膜对ＡＢＡ的结合活性，盐胁迫、渗透胁迫、干旱胁迫和热冲激处理分别使结合活性上升３４．９％、１７．８％、２３．１％和１３．３％。
Microvolume radioactivity ligand binding assay indicated that there were ABA binding sites in microsomes from maize roots. The amount of ABA bound was maximal at pH 6. 5 (Fig. 2) and the activity was insensitive to temperature difference between 0℃ and 25℃(Fig. 1 ). After 5 min the amount bound reached 50% of the maximum value, which was reached after 30min, and remained unchanged for 60min (Fig. 1). Trypsin digestion experiment (Fig. 4) showed that the binding sites were on the protein. The freezingthawing experiment showed that the activity of ABA binding protein depended not only on its own characteristic structure but also on some special membrane lipid micro-environment. Specific binding activity Can be reduced by the reducing agent dithioerythritol (Fig. 5).The results suggest that a reducible group, possibly a disulfide group, may be located at or near the binding site and are required for its action. The specific binding could be enhanced by stress treatment. Salt stress, osmotic stress,drought stress and heat shock treatment all increased specific binding activity,the extents of increase being 34. 9,17. 8, 23. 1 and 13. 3% respectively (Fig. 6).
基金
国家自然科学基金
关键词
玉米
微粒体
脱落酸
结合蛋白
微粒体
逆境胁迫
binding protein, ABA specific binding,environment stress, ABA, microsome
