Yang Zhenle, Su Xinhua, Wu Feng, Gong Yandao, Kuang Tingyun
Key Laboratory of Photosynthesis and Environment Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, PR China.
Biophys Chem. 2005 May 1;115(1):19-27. doi: 10.1016/j.bpc.2005.01.004. Epub 2005 Jan 19.
Phosphatidylglycerol (PG) is the only anionic phospholipid in photosynthetic membrane. In this study, photosystem I (PSI) particles obtained from plant spinach were reconstituted into PG liposomes at a relatively high concentration. The results from visible absorption, fluorescence emission, and circular dichroism (CD) spectra reveal an existence of the interactions of PSI with PG. PG effect causes blue-shift and intensity decrease of Chl a peak bands in the absorption and 77 K fluorescence emission. The visible CD spectra indicate that the excitonic interactions for Chl a and Chl b molecules were enhanced upon reconstitution. Furthermore, more or less blue- or red-shift of the peaks characterized by Chl a, Chl b, and carotenoid molecules are also occurred. Simultaneously, an increase in alpha-helix and a decrease particularly in the disordered conformations of protein secondary structures are observed. In addition, the same effect also leads to somewhat more tryptophan (Trp) residues exposed to the polar environment. These results demonstrate that some alteration of molecular organization occurs within both the external antenna LHCI and PSI core complex after PSI reconstitution.
磷脂酰甘油（PG）是光合膜中唯一的阴离子磷脂。在本研究中，从植物菠菜中获得的光系统I（PSI）颗粒以相对较高的浓度重组成PG脂质体。可见吸收光谱、荧光发射光谱和圆二色性（CD）光谱的结果揭示了PSI与PG之间存在相互作用。PG效应导致吸收光谱和77K荧光发射光谱中叶绿素a峰带发生蓝移和强度降低。可见CD光谱表明，重组后叶绿素a和叶绿素b分子的激子相互作用增强。此外，叶绿素a、叶绿素b和类胡萝卜素分子特征峰或多或少也发生了蓝移或红移。同时，观察到蛋白质二级结构的α-螺旋增加，特别是无序构象减少。此外，相同的效应还导致更多的色氨酸（Trp）残基暴露于极性环境中。这些结果表明，PSI重组后，外部天线LHCI和PSI核心复合物的分子组织均发生了一些改变。
