蓝隐藻叶绿素蛋白复合物的圆二色谱特性

Circular Dichroism Spectra Characteristics of Chlorophyll-Protein Complexes from Chroomonas placoidea

采用蔗糖密度梯度离心分离的方法,从蓝隐藻(Chroomonas placoidea)中稳定分离到了4种活性的叶绿素蛋白复合物,分别为2种捕光复合物、1种PSⅡ颗粒和1种PSⅠ颗粒.采用圆二色谱技术对分离到的复合物进行了全波段(190~750 nm)光谱测定,结果显示:①远紫外区:二级结构预测表明各复合物的无规卷曲比例相近,约占30%左右;PSⅠ颗粒和1种PSⅡ和捕光复合物含有更高比例的α-螺旋和β-转角,但几乎不存在β-折叠.②近紫外区:在芳香族氨基酸的三级结构信号区,各复合物均未观测到Tyr的信号峰.③可见光区:690 nm附近信号峰的有无是隐藻捕光复合物和中心复合物的一个区别.实验结果不仅给出了隐藻叶绿素蛋白复合物性质的新信息,也为今后叶绿素蛋白复合物的分析和鉴定提供了新的光谱鉴定依据.

By using the method of sucrose density gradient centrifugation, four types of active chlorophyll protein complexes are isolated routinely from Chroomonas placoidea, among which are two types of light harvesting comple-xes, one types of PSⅡparticle and one types of PSⅠparticle. Method of circular dichroism is used to carry out a full band (190-750 nm) spectrum measurement of complexes and the results show that:①In the far UV region, the proportion of random coil in each complex is similar, which accounts for about 30% according to secondary structure prediction. There exists higher proportion of α-helix and β-turn in PSⅠparticle than in PSⅡparticle and light harvesting complexes, but hardly anyβ-sheet is detected. ②In the near UV region, no signal peak of Tyr is observed in any complexes in tertiary structure of aromatic amino acids. ③In the visible light region, the presence and absence of a signal peak discriminate the light harvesting complexes and the core complexes in cryptophytic al-ga. These results can provide not only new information of the characteristics of chlorophyll protein complexes from cryptophytic alga, but also new foundation for the analysis and identification of chlorophyll protein complexes.