Durchan Milan, Keşan Gürkan, Slouf Václav, Fuciman Marcel, Staleva Hristina, Tichý Josef, Litvín Radek, Bína David, Vácha František, Polívka Tomáš
Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic; Institute of Plant Molecular Biology, Biology Centre, Academy of Sciences of the Czech Republic, České Budějovice, Czech Republic.
Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic.
Biochim Biophys Acta. 2014 Oct;1837(10):1748-55. doi: 10.1016/j.bbabio.2014.06.001. Epub 2014 Jun 10.
We report on energy transfer pathways in the main light-harvesting complex of photosynthetic relative of apicomplexan parasites, Chromera velia. This complex, denoted CLH, belongs to the family of FCP proteins and contains chlorophyll (Chl) a, violaxanthin, and the so far unidentified carbonyl carotenoid related to isofucoxanthin. The overall carotenoid-to-Chl-a energy transfer exhibits efficiency over 90% which is the largest among the FCP-like proteins studied so far. Three spectroscopically different isofucoxanthin-like molecules were identified in CLH, each having slightly different energy transfer efficiency that increases from isofucoxanthin-like molecules absorbing in the blue part of the spectrum to those absorbing in the reddest part of spectrum. Part of the energy transfer from carotenoids proceeds via the ultrafast S2 channel of both the violaxanthin and isofucoxanthin-like carotenoid, but major energy transfer pathway proceeds via the S1/ICT state of the isofucoxanthin-like carotenoid. Two S1/ICT-mediated channels characterized by time constants of ~0.5 and ~4ps were found. For the isofucoxanthin-like carotenoid excited at 480nm the slower channel dominates, while those excited at 540nm employs predominantly the fast 0.5ps channel. Comparing these data with the excited-state properties of the isofucoxanthin-like carotenoid in solution we conclude that, contrary to other members of the FCP family employing carbonyl carotenoids, CLH complex suppresses the charge transfer character of the S1/ICT state of the isofucoxanthin-like carotenoid to achieve the high carotenoid-to-Chl-a energy transfer efficiency.
我们报道了顶复门寄生虫的光合相对物——维氏色球藻主要光捕获复合物中的能量转移途径。这种复合物称为CLH，属于FCP蛋白家族，含有叶绿素a、紫黄质以及迄今为止尚未鉴定出的与异岩藻黄素相关的羰基类胡萝卜素。总的类胡萝卜素到叶绿素a的能量转移效率超过90%，这是迄今为止研究的FCP样蛋白中最高的。在CLH中鉴定出三种光谱不同的异岩藻黄素样分子，每种分子的能量转移效率略有不同，从在光谱蓝色部分吸收的异岩藻黄素样分子到在光谱最红色部分吸收的分子，能量转移效率逐渐增加。类胡萝卜素的部分能量转移通过紫黄质和异岩藻黄素样类胡萝卜素的超快S2通道进行，但主要的能量转移途径通过异岩藻黄素样类胡萝卜素的S1/ICT状态进行。发现了两个以0.5和4皮秒的时间常数为特征的S1/ICT介导通道。对于在480nm激发的异岩藻黄素样类胡萝卜素，较慢的通道占主导，而在540nm激发的则主要采用快速的0.5皮秒通道。将这些数据与溶液中异岩藻黄素样类胡萝卜素的激发态性质进行比较，我们得出结论，与使用羰基类胡萝卜素的FCP家族其他成员相反，CLH复合物抑制了异岩藻黄素样类胡萝卜素S1/ICT状态的电荷转移特性，以实现高的类胡萝卜素到叶绿素a的能量转移效率。
