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首页> 美国卫生研究院文献>The Journal of Biological Chemistry >Fluorescence lifetime analyses reveal how the high light–responsive protein LHCSR3 transforms PSII light-harvesting complexes into an energy-dissipative state
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Fluorescence lifetime analyses reveal how the high light–responsive protein LHCSR3 transforms PSII light-harvesting complexes into an energy-dissipative state

机译：荧光寿命分析揭示了高光响应蛋白LHCSR3如何将PSII捕光复合物转化为耗能状态

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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 PSII—LHCII–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.
机译：在绿藻中，与光应力有关的复杂应力相关3（LHCSR3）负责吸收光能的pH依赖性消散，这对于在高光条件下的生存至关重要。 LHCSR3结合光系统II和光捕获复合体II（PSII–LHCII）超复合体，并在酸性条件下将其转化为能量耗散形式，但分子机制仍不清楚。在这里，我们显示了在绿藻莱茵衣藻中，LHCSR3调节激发能流，并在PSII超复合物的光捕获复合物中消散激发能。使用荧光衰减相关光谱分析，我们发现，当PSII超复合物在强光条件下与LHCSR3结合时，与从CP47到CP47相比，从捕光复合物到叶绿素结合蛋白CP43的激发能转移受到选择性抑制。反应中心超负荷产生的过量激发能。通过分析飞秒上转换的荧光动力学，我们进一步发现PSII-LHCII-LHCSR3超复合物的pH和LHCSR3依赖性猝灭伴随着以684 nm为中心的荧光发射，其衰减时间常数为18.6 ps，即等于叶绿素-叶黄素异二聚体中产生的叶黄素自由基阳离子的上升时间常数。这些结果表明了一种机制，其中LHCSR3将PSII超复合物转化为能量耗散状态，并为依赖LHCSR3的能量猝灭中的分子事件和特征提供了重要的见识。

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