Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic.
1] Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic. [2] Institute of Microbiology, Academy of Sciences of the Czech Republic, Třeboň, Czech Republic.
Nat Chem Biol. 2015 Apr;11(4):287-91. doi: 10.1038/nchembio.1755. Epub 2015 Feb 23.
Plants collect light for photosynthesis using light-harvesting complexes (LHCs)-an array of chlorophyll proteins that are able to reversibly switch from harvesting to energy-dissipation mode to prevent damage of the photosynthetic apparatus. LHC antennae as well as other members of the LHC superfamily evolved from cyanobacterial ancestors called high light-inducible proteins (Hlips). Here, we characterized a purified Hlip family member HliD isolated from the cyanobacterium Synechocystis sp. PCC 6803. We found that the HliD binds chlorophyll-a (Chl-a) and β-carotene and exhibits an energy-dissipative conformation. Using femtosecond spectroscopy, we demonstrated that the energy dissipation is achieved via direct energy transfer from a Chl-a Qy state to the β-carotene S1 state. We did not detect any cation of β-carotene that would accompany Chl-a quenching. These results provide proof of principle that this quenching mechanism operates in the LHC superfamily and also shed light on the photoprotective role of Hlips and the evolution of LHC antennae.
植物利用光捕获复合物（LHCs）收集用于光合作用的光——一组能够可逆地从捕获模式切换到能量耗散模式的叶绿素蛋白，以防止光合作用装置的损坏。LHC 天线以及 LHC 超家族的其他成员是从称为高光诱导蛋白（Hlips）的蓝细菌祖先中进化而来的。在这里，我们对从蓝细菌集胞藻 PCC 6803 中分离出的纯化 Hlip 家族成员 HliD 进行了表征。我们发现 HliD 结合叶绿素-a（Chl-a）和β-胡萝卜素，并表现出能量耗散构象。使用飞秒光谱学，我们证明能量耗散是通过从 Chl-a Qy 态到β-胡萝卜素 S1 态的直接能量转移来实现的。我们没有检测到任何伴随 Chl-a 猝灭的β-胡萝卜素阳离子。这些结果为这一猝灭机制在 LHC 超家族中起作用提供了原理上的证明，也揭示了 Hlips 的光保护作用和 LHC 天线的进化。
