Dynamical and allosteric regulation of photoprotection in light harvesting complex II.
Dynamical and allosteric regulation of photoprotection in light harvesting complex II.
复制标题
光捕获复合物 II 中光保护的动态和变构调节
DOI：
10.1007/s11426-020-9771-2
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发表时间：
2020-08
期刊：
影响因子：
--
通讯作者：
Weng Y
中科院分区：
文献类型：
--
作者：
Li H;Wang Y;Ye M;Li S;Li D;Ren H;Wang M;Du L;Li H;Veglia G;Gao J;Weng Y
光系统II的主要捕光复合物（LHCII）在捕光和激发能量耗散中起双重作用，以保护光损伤免受过量能量的伤害。调节开关是由酸度增加、温度升高或两者共同引起的。然而，在原子水平上的蛋白质动力学的分子起源仍然是未知的。我们进行了温度跳跃时间分辨红外光谱和分子动力学模拟，以确定LHCII三聚体的能量猝灭动力学和构象变化。我们发现，自发形成的一对局部α-螺旋从310-螺旋E/环和C-末端卷曲的相邻单体，在响应于增加的环境温度和/或酸度，诱导剪切运动的跨膜螺旋A和B，移动构象平衡到一个更开放的状态，与相关的类胡萝卜素之间的角度增加。类胡萝卜素叶黄素1的动态变构构象变化导致其第一激发态与叶绿素色素紧密接触，促进荧光猝灭。基于这些结果，我们提出了一个统一的机制，通过该机制LHCII三聚体控制多余的激发能的耗散，以响应温度和酸度的增加，作为一个内在的结果，强烈的阳光在植物光合作用。
Major light-harvesting complex of photosystem II (LHCII) plays a dual role in light-harvesting and excited energy dissipation to protect photodamage from excess energy. The regulatory switch is induced by increased acidity, temperature or both. However, the molecular origin of the protein dynamics at the atomic level is still unknown. We carried out temperature-jump time-resolved infrared spectroscopy and molecular dynamics simulations to determine the energy quenching dynamics and conformational changes of LHCII trimers. We found that the spontaneous formation of a pair of local α-helices from the 310-helix E/loop and the C-terminal coil of the neighboring monomer, in response to the increased environmental temperature and/or acidity, induces a scissoring motion of transmembrane helices A and B, shifting the conformational equilibrium to a more open state, with an increased angle between the associated carotenoids. The dynamical allosteric conformation change leads to close contacts between the first excited state of carotenoid lutein 1 and chlorophyll pigments, facilitating the fluorescence quenching. Based on these results, we suggest a unified mechanism by which the LHCII trimer controls the dissipation of excess excited energy in response to increased temperature and acidity, as an intrinsic result of intense sun light in plant photosynthesis.
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