Di Valentin Marilena, Meneghin Elena, Orian Laura, Polimeno Antonino, Büchel Claudia, Salvadori Enrico, Kay Christopher W M, Carbonera Donatella
Department of Chemical Sciences, University of Padua, via Marzolo 1, 35131 Padova, Italy.
Biochim Biophys Acta. 2013 Oct;1827(10):1226-34. doi: 10.1016/j.bbabio.2013.07.003. Epub 2013 Jul 13.
Although the major light harvesting complexes of diatoms, called FCPs (fucoxanthin chlorophyll a/c binding proteins), are related to the cab proteins of higher plants, the structures of these light harvesting protein complexes are much less characterized. Here, a structural/functional model for the "core" of FCP, based on the sequence homology with LHCII, in which two fucoxanthins replace the central luteins and act as quenchers of the Chl a triplet states, is proposed. Combining the information obtained by time-resolved EPR spectroscopy on the triplet states populated under illumination, with quantum mechanical calculations, we discuss the chlorophyll triplet quenching in terms of the geometry of the chlorophyll-carotenoid pairs participating to the process. The results show that local structural rearrangements occur in FCP, with respect to LHCII, in the photoprotective site.
尽管硅藻的主要光捕获复合体，即所谓的FCP（岩藻黄质叶绿素a/c结合蛋白），与高等植物的cab蛋白相关，但这些光捕获蛋白复合体的结构特征要少得多。在此，基于与LHCII的序列同源性，提出了一个FCP“核心”的结构/功能模型，其中两个岩藻黄质取代了中心叶黄素，并作为叶绿素a三线态的猝灭剂。结合通过时间分辨EPR光谱获得的关于光照下产生的三线态的信息，以及量子力学计算，我们根据参与该过程的叶绿素-类胡萝卜素对的几何结构来讨论叶绿素三线态猝灭。结果表明，相对于LHCII，FCP在光保护位点发生了局部结构重排。
