Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy.
Biology Centre, Czech Academy of Sciences, Institute of Plant Molecular Biology, Branišovská 1160/31, 370 05 České Budějovice, Czech Republic.
Int J Mol Sci. 2022 Apr 27;23(9):4812. doi: 10.3390/ijms23094812.
Carotenoids represent the first line of defence of photosystems against singlet oxygen (O) toxicity, because of their capacity to quench the chlorophyll triplet state (Chl) through a physical mechanism based on the transfer of triplet excitation (triplet-triplet energy transfer, TTET). In previous works, we showed that the antenna LHCII is characterised by a robust photoprotective mechanism, able to adapt to the removal of individual chlorophylls while maintaining a remarkable capacity for Chl quenching. In this work, we investigated the effects on this quenching induced in LHCII by the replacement of the lutein bound at the L1 site with violaxanthin and zeaxanthin. We studied LHCII isolated from the mutants -in which lutein is replaced by violaxanthin-and , in which all xanthophylls are replaced constitutively by zeaxanthin. We characterised the photophysics of these systems via optically detected magnetic resonance (ODMR) and time-resolved electron paramagnetic resonance (TR-EPR). We concluded that, in LHCII, lutein-binding sites have conserved characteristics, and ensure efficient TTET regardless of the identity of the carotenoid accommodated.
类胡萝卜素是光合作用系统抵御单线态氧 (O) 毒性的第一道防线，因为它们能够通过基于三重态激发转移（三重态-三重态能量转移，TTET）的物理机制猝灭叶绿素三重态（Chl）。在之前的工作中，我们表明天线 LHCII 具有强大的光保护机制，能够在去除单个叶绿素的同时保持显著的 Chl 猝灭能力。在这项工作中，我们研究了用叶黄素取代 LHCII 中的 L1 位上的叶黄素以及用 violaxanthin 和 zeaxanthin 取代的叶黄素对 LHCII 中这种猝灭的影响。我们研究了从突变体中分离出的 LHCII-在其中叶黄素被 violaxanthin 取代-和 ，其中所有的叶黄素都被 zeaxanthin 组成性取代。我们通过光学检测磁共振（ODMR）和时间分辨电子顺磁共振（TR-EPR）对这些系统的光物理性质进行了表征。我们得出结论，在 LHCII 中，叶黄素结合位点具有保守的特征，并且无论容纳的类胡萝卜素的身份如何，都能确保有效的 TTET。
