Harrison M A, Allen J F
Department of Pure and Applied Biology, University of Leeds, England.
Eur J Biochem. 1992 Mar 15;204(3):1107-14. doi: 10.1111/j.1432-1033.1992.tb16735.x.
A material containing only photosystem I (PSI) and the chlorophyll-a/b-binding light-harvesting complex of PSII (LHC-II) has been isolated from the chloroplast thylakoid membrane by solubilization with Triton X-100. Fluorescence spectroscopy shows that, within the material, LHC-II is coupled to PSI for excitation-energy transfer and that this coupling is decreased by the presence of Mg2+, which also decreased PSI electron transport specifically at limiting light intensity. Inclusion of phosphorylated LHC-II within the material did not alter its structure, but gave decreased energy transfer to PSI and inhibition of electron transport which was independent of light intensity, implying effects of phosphorylation on both light harvesting and directly on electron transport. Inclusion of Mg2+ within the phosphorylated material gave decreased energy transfer, but slightly increased PSI electron transport. A cation-induced direct promotion of PSI electron transport was also observed in isolated PSI particles. The PSI/LHC-II material represents a model system for examining protein interactions during light-state adaptations and the possibility that LHC-II can contribute to the antenna of PSI in light state 2 in vivo is discussed.
通过用Triton X-100溶解，从叶绿体类囊体膜中分离出了一种仅包含光系统I（PSI）和光系统II（PSII）的叶绿素a/b结合捕光复合体（LHC-II）的材料。荧光光谱表明，在该材料中，LHC-II与PSI耦合用于激发能量传递，并且这种耦合会因Mg2+的存在而降低，Mg2+还会在低光强下特异性地降低PSI电子传递。在材料中加入磷酸化的LHC-II不会改变其结构，但会减少向PSI的能量传递并抑制与光强无关的电子传递，这意味着磷酸化对捕光和直接对电子传递都有影响。在磷酸化材料中加入Mg2+会减少能量传递，但会使PSI电子传递略有增加。在分离的PSI颗粒中也观察到阳离子对PSI电子传递的直接促进作用。PSI/LHC-II材料是用于研究光状态适应过程中蛋白质相互作用的模型系统，并讨论了LHC-II在体内光状态2中可能对PSI天线有贡献的可能性。
