Light-induced isomerization of the LHCII-bound xanthophyll neoxanthin: possible implications for photoprotection in plants.
Light-induced isomerization of the LHCII-bound xanthophyll neoxanthin: possible implications for photoprotection in plants.
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DOI：
10.1016/j.bbabio.2011.06.011
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发表时间：
2011-09
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影响因子：
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通讯作者：
M. Zubik;R. Luchowski;W. Grudziński;M. Gospodarek;I. Gryczynski;Z. Gryczynski;J. Dobrucki;W. Gruszecki
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作者：
M. Zubik;R. Luchowski;W. Grudziński;M. Gospodarek;I. Gryczynski;Z. Gryczynski;J. Dobrucki;W. Gruszecki
光系统II捕光色素蛋白复合物（LHCII）是植物中最大的光合天线复合物，也是生物圈中含量最丰富的膜蛋白。植物的适应性和生产力直接取决于光合机构中由捕获的光量子产生的激发与光化学过程速率之间的平衡。过量的激发能量导致光合装置和整个生物体的氧化损伤，因此激发密度和光合作用之间的平衡需要精确和有效的调节，也在天线复合物的水平上操作。我们发现，照明的分离LHCII导致异构化的蛋白质结合的新黄质从构象9′-顺式9′，13-和9′，13 ′-双形式。同时观察到光驱动的激发猝灭，表现为叶绿素a荧光强度的降低和荧光寿命的缩短。这两个过程，新黄质异构化和叶绿素激发淬灭，在昏暗的光是可逆的。LHCII的77 K荧光测量结果表明，光照与低能态的出现有关，低能态可以作为过度激发的色素-蛋白质复合物中的能量陷阱。提出了分子事件的可能顺序，导致保护性的过量激发能猝灭：新黄素光异构化→形成LHCII超分子结构，这增强了能量陷阱的产生→激发猝灭。
Light-harvesting pigment-protein complex of Photosystem II (LHCII) is the largest photosynthetic antenna complex of plants and the most abundant membrane protein in the biosphere. Plant fitness and productivity depend directly on a balance between excitations in the photosynthetic apparatus, generated by captured light quanta, and the rate of photochemical processes. Excess excitation energy leads to oxidative damage of the photosynthetic apparatus and entire organism and therefore the balance between the excitation density and photosynthesis requires precise and efficient regulation, operating also at the level of antenna complexes. We show that illumination of the isolated LHCII leads to isomerization of the protein-bound neoxanthin from conformation 9′-cis to 9′,13- and 9′,13′-dicis forms. At the same time light-driven excitation quenching is observed, manifested by a decrease in chlorophyll a fluorescence intensity and shortened fluorescence lifetimes. Both processes, the neoxanthin isomerization and the chlorophyll excitation quenching, are reversible in dim light. The results of the 77K florescence measurements of LHCII show that illumination is associated with appearance of the low-energy states, which can serve as energy traps in the pigment–protein complex subjected to excess excitation. Possible sequence of the molecular events is proposed, leading to a protective excess excitation energy quenching: neoxanthin photo-isomerization→formation of LHCII supramolecular structures which potentiate creation of energy traps→excitation quenching.