Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts.
Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, United Kingdom.
Biophys J. 2021 Aug 3;120(15):3091-3102. doi: 10.1016/j.bpj.2021.06.010. Epub 2021 Jun 30.
In green plants, light harvesting complex of Photosystem II (LHCII) absorbs and transports excitation energy toward the photosynthetic reaction centers and serves as a site for energy-dependent nonphotochemical quenching (qE), the photoprotective dissipation of energy as heat. LHCII is thought to activate dissipation through conformational changes that change the photophysical behaviors. Understanding this balance requires a characterization of how the conformations of LHCII, and thus its photophysics, are influenced by individual factors within the membrane environment. Here, we used ensemble and single-molecule fluorescence to characterize the excited-state lifetimes and switching kinetics of LHCII embedded in nanodisc- and liposome-based model membranes of various sizes and lipid compositions. As the membrane area decreased, the quenched population and the rate of conformational dynamics both increased because of interactions with other proteins, the aqueous solution, and/or disordered lipids. Although the conformational states and dynamics were similar in both thylakoid and asolectin lipids, photodegradation increased with thylakoid lipids, likely because of their charge and pressure properties. Collectively, these findings demonstrate the ability of membrane environments to tune the conformations and photophysics of LHCII.
在绿色植物中，光系统 II（PSII）的光捕获复合物（LHCII）吸收和传输激发能到光合作用反应中心，并作为能量依赖性非光化学猝灭（qE）的位点，即能量作为热量的光保护耗散。LHCII 被认为通过改变光物理行为的构象变化来激活耗散。理解这种平衡需要表征 LHCII 的构象以及其光物理性质如何受到膜环境中单个因素的影响。在这里，我们使用集合和单分子荧光来表征嵌入在具有不同大小和脂质组成的纳米盘和脂质体模型膜中的 LHCII 的激发态寿命和转换动力学。随着膜面积的减小，由于与其他蛋白质、水溶液和/或无序脂质的相互作用，猝灭的群体和构象动力学的速率都增加了。尽管在类囊体和大豆卵磷脂脂质中，构象状态和动力学相似，但由于类囊体脂质的电荷和压力特性，光降解增加了。总的来说，这些发现表明膜环境能够调节 LHCII 的构象和光物理性质。
