Fluorescence lifetime analyses reveal how the high light-responsive protein LHCSR3 transforms PSII light-harvesting complexes into an energy-dissipative state
Fluorescence lifetime analyses reveal how the high light-responsive protein LHCSR3 transforms PSII light-harvesting complexes into an energy-dissipative state
复制标题
DOI：
10.1074/jbc.m117.805192
复制
发表时间：
2017-11-17
影响因子：
4.8
通讯作者：
Minagawa, Jun
中科院分区：
文献类型：
--
作者：
Kim, Eunchul;Akimoto, Seiji;Minagawa, Jun
在绿色藻类中，捕光复合应激相关蛋白3（LHCSR 3）负责吸收光能的pH依赖性耗散，这是在强光条件下生存的重要功能。LHCSR 3结合光系统II和捕光复合物II（PSII-LHCII）超复合物，并在酸性条件下将其转化为能量耗散形式，但分子机制尚不清楚。在这里，我们表明，在绿色的莱茵衣藻，LHCSR 3调制的激发能流和耗散的光捕获复合物的PSII超复合物内的激发能。使用荧光衰减相关光谱分析，我们发现，当PSII超复合物与LHCSR 3在强光条件下，从捕光复合物的叶绿素结合蛋白CP 43的激发能量转移被选择性地抑制相比，CP 47，防止多余的激发能量超载的反应中心。通过分析飞秒上转换荧光动力学，我们进一步发现，pH值和LHCSR 3的PSIILHCII-LHCSR 3超复合物的依赖性淬灭伴随着荧光发射中心在684 nm，衰减时间常数为18.6 ps，这是相当于上升时间常数的叶黄素自由基阳离子内产生的叶绿素-叶黄素异二聚体。这些结果表明，LHCSR 3的PSII超复合物转化为能量耗散状态的机制，并提供关键的洞察LHCSR 3依赖的能量淬火的分子事件和特性。
In green algae, light-harvesting complex stress-related 3 (LHCSR3) is responsible for the pH-dependent dissipation of absorbed light energy, a function vital for survival under high-light conditions. LHCSR3 binds the photosystem II and light-harvesting complex II (PSII-LHCII) supercomplex and transforms it into an energy-dissipative form under acidic conditions, but the molecular mechanism remains unclear. Here we show that in the green alga Chlamydomonas reinhardtii, LHCSR3 modulates the excitation energy flow and dissipates the excitation energy within the light-harvesting complexes of the PSII supercomplex. Using fluorescence decay-associated spectra analysis, we found that, when the PSII supercomplex is associated with LHCSR3 under high-light conditions, excitation energy transfer from light-harvesting complexes to chlorophyll-binding protein CP43 is selectively inhibited compared with that to CP47, preventing excess excitation energy from overloading the reaction center. By analyzing femtosecond up-conversion fluorescence kinetics, we further found that pH- and LHCSR3-dependent quenching of the PSIILHCII-LHCSR3 supercomplex is accompanied by a fluorescence emission centered at 684 nm, with a decay time constant of 18.6 ps, which is equivalent to the rise time constant of the lutein radical cation generated within a chlorophyll-lutein heterodimer. These results suggest a mechanism in which LHCSR3 transforms the PSII supercomplex into an energy-dissipative state and provide critical insight into the molecular events and characteristics in LHCSR3-dependent energy quenching.