水稻巯基蛋白酶抑制剂的圆二色谱研究  

Circular Dichroism Studies of Cysteine Proteinase Inhibitor From Rice

作　　者：荣艳珍[1] 赵曦[1] 常丽青[1] 高顺[1] 李宜瑾[1] 吕鸿周[1] 王陈继[1] 鲍锦库[1] 

机构地区：[1]四川大学生命科学学院,成都610064

出　　处：《四川大学学报（自然科学版）》2005年第1期162-166,共5页Journal of Sichuan University(Natural Science Edition)

摘　　要：水稻巯基蛋白酶抑制剂(CPI)圆二色性谱(CD)显示206nm和222nm处的双负峰,CPI分子以α 螺旋构象为主;当CPI与木瓜蛋白酶等摩尔结合后,CPI完全丧失抑制活性,复合物CD谱发生显著变化,α 螺旋含量降低.CPI具有较高的结构稳定性,但在100℃处理时间延长以及pH向酸碱两极变化时,其CD谱发生较大改变,α 螺旋含量减少;而抑制活性仅在pH>9时逐渐下降,在酸性条件下保持不变.用不同试剂修饰CPI分子中的巯基和二硫键,CPI的活性不受影响;DTT、PCMB修饰CPI,其CD谱发生显著变化,NEM修饰CPI,其CD谱变化甚微.4mol/L的脲中,CD谱仅显示206nm负峰、214nm和225～235nm处新的负肩,并在240～250nm之间出现新的负峰,分子中无规卷曲增加,CPI活性未受影响;经NBS修饰,CPI分子中α 螺旋减少,无规卷曲增加较多,CPI完全丧失抑制活性.Circular dichroism(CD) spectrum of cysteine proteinase inhibitor(CPI) displayed two negative peaks on 206nm and 222nm, indicating that the main secondary structure of CPI was α-helix. When acted with equal proportion of Papain , the inhibiting activity of CPI lost completely; CD spectrum changed remarkably and the content of α-helix declined. CPI structure was relatively stable , But when treated at 100℃ longer or as pH varied toward acid and alkali, CD spectra of CPI changed significantly, the content of α-helix decreased, while CPI activity remained unchanged in acid condition ,only when pH >9.0, it lost gradually. Modification of sulfhydryl groups and disulfide bond in CPI with various chemical reagents had no effect on its activity, CD spectrum of the NEM-modified CPI changed little. After modification with PCMB and DTT ,CD spectra of CPI showed remarkable change. In the presence of 4mol/L urea, CD spectrum of CPI only displayed the negative band at 206nm with new negative shoulders at 214nm and around 225nm～235nm as well as a new negative band between 240nm and 250nm. Although the CPI activity hadn't been affected, the content of random coiling in the molecular increased. Modification of CPI with NBS in the presence of 4M urea led to the decrease of the content of αhelix as well as the great increase of random coiling, followed by an almost complete loss of CPI activity.

关 键 词：抑制剂 巯基蛋白酶抑制剂 分子修饰 抑制活性 圆二色性 

分 类 号：Q503[生物学—生物化学]