Specificity of light-harvesting systems of chromophytes in reference to their energy migration

为了解岩藻黄质在多种类胡萝卜素中被用于有色藻类捕光的原因，尝试用不同种类的类胡萝卜素取代岩藻黄质-叶绿素a/c蛋白中的岩藻黄质分子，并分析它们向叶绿素a的激发能转移。用无水乙醚处理纯化和冻干的岩藻黄质-叶绿素a/c蛋白，得到去除岩藻黄质的蛋白质制剂，其中最初结合的4种岩藻黄质中的3种被去除。该蛋白保留了2个叶绿素a，但在叶绿素c和叶绿素a之间的激发能迁移在该蛋白中几乎看不到。当这种岩藻黄质耗尽的蛋白质与岩藻黄质在0.1%的月桂基蔗糖中孵育时，岩藻黄质以能够将激发能迁移到叶绿素a的形式并入蛋白质中，同时在从叶绿素c到a的能量耦合中恢复。β-胡萝卜素和玉米黄质也掺入到该蛋白质中，但没有显示出这些能量偶联的任何恢复，而从Ruttnera（附着植物）分离的19 ′-己酰基氧基岩藻黄质和从Symbionidium（甲藻）分离的多甲藻素都没有掺入到该蛋白质中，表明该蛋白质的岩藻黄质结合结构域对岩藻黄质不是高度特异性的，但在结构上不适合于类胡萝卜素的修饰形式。

To understand why, among a vrieties of carotenoid species, fucoxanthin is used for the light-harvesting in chromophyte algae, an attempt was made to replace the fucoxanthin molecules in fucoxanthin-chlorophyll a/c protein with different species of carotenoids and to analyze their excitation energy transfer to chlorophyll a. Treatment of purified and lyophyrized fucoxanthin-chlorophyll a/c protein from Ectocarpus (pheophyte) with anhydrous diethylether, a fucoxanthin-depleted protein preparation was obtained, in which three of 4 fucoxanthins originally bound were removed. This protein retained 2 chlorophyll a's but the excitation energy migration both between fucoxanthin and chlorophyll a between chlorophyll c and chlorophyll a were hardly seen in this protein. When this fucoxanthin-depleted protein was incubated with fucoxanthin in 0.1% lauryl sucrose, fucoxanthin was incoporated into protein in the form competent in excitation energy migration to chlorophyll a, and simultaneously regained in the energetic coupling from chlorophyll c to a. beta-Carotene and zeaxanthin were also incorporated into this protein but without showing any recovery of these energetic coupling, while neither 19'-hexanoyl oxyfucoxanthin isolated from Ruttnera (haptophyte) nor peridinin isolated from Symbionidium (dinophyte) was incorporated in this protein, indicating the fucoxanthin-binding domain of this protein is not highly specific to fucoxanthin but is not structurally fitted to modifid forms of carotenoids.