School of Biological and Chemical Sciences, Queen Mary University of London, Mile End, London E1 4NS, United Kingdom.
Laboratory of Biophysics, Wageningen University & Research, P.O. Box 8128, 6708WE Wageningen, The Netherlands.
Biochim Biophys Acta Bioenerg. 2018 Jul;1859(7):471-481. doi: 10.1016/j.bbabio.2018.03.015. Epub 2018 Apr 4.
The bioenergetics of light-harvesting by photosynthetic antenna proteins in higher plants is well understood. However, investigation into the regulatory non-photochemical quenching (NPQ) mechanism, which dissipates excess energy in high light, has led to several conflicting models. It is generally accepted that the major photosystem II antenna protein, LHCII, is the site of NPQ, although the minor antenna complexes (CP24/26/29) are also proposed as alternative/additional NPQ sites. LHCII crystals were shown to exhibit the short excitation lifetime and several spectral signatures of the quenched state. Subsequent structure-based models showed that this quenching could be explained by slow energy trapping by the carotenoids, in line with one of the proposed models. Using Fluorescence Lifetime Imaging Microscopy (FLIM) we show that the crystal structure of CP29 corresponds to a strongly quenched conformation. Using a structure-based theoretical model we show that this quenching may be explained by the same slow, carotenoid-mediated quenching mechanism present in LHCII crystals.
高等植物中光合天线蛋白的光捕获生物能量学已得到很好的理解。然而，对过剩能量耗散的调节非光化学猝灭（NPQ）机制的研究导致了几个相互矛盾的模型。普遍认为，主要的光合系统 II 天线蛋白 LHCII 是 NPQ 的位点，尽管较小的天线复合物（CP24/26/29）也被提议为替代/附加 NPQ 位点。LHCII 晶体表现出短的激发寿命和几个猝灭状态的光谱特征。随后的基于结构的模型表明，这种猝灭可以通过类胡萝卜素的缓慢能量捕获来解释，这与其中一个提出的模型一致。使用荧光寿命成像显微镜（FLIM），我们表明 CP29 的晶体结构对应于一个强烈猝灭的构象。使用基于结构的理论模型，我们表明这种猝灭可以通过在 LHCII 晶体中存在的相同的缓慢、类胡萝卜素介导的猝灭机制来解释。
