JBC：光合作用研究取得新进展

近日，山东大学微生物技术国家重点实验室、山东大学海洋生物技术研究中心张玉忠教授与荷兰莱顿大学Thijs J. Aartsma教授等合作在光合作用研究方面取得了重要进展，其研究成果在12月12日以封面文章的形式发表在国际知名杂志《生物化学杂志》(Journal of Biological Chemistry)上。

多年来，国内外一直用透射电子显微镜技术研究藻胆体的结构，但透射电子显微镜观察的是样品的二维结构。张玉忠教授课题组刘鲁宁等人，利用原子力显微镜技术，首次从纳米尺度上，直接观察到了单细胞红藻——紫球藻天然状态下藻胆体的三维形貌(64×42×28nm)(长×宽×高)及其在类囊体膜上的排列格式。研究发现紫球藻藻胆体在类囊体膜上的排列格式具有多样性，更有意义的是，各种不同排列格式中，藻胆体在类囊体膜上的排列都是非常拥挤的。此外，张玉忠教授与荷兰莱顿大学 Thijs J. Aartsma教授等合作，利用单分子光谱技术，发现强光下紫球藻通过藻胆体内部能量传递解偶联，来实现过多光能的耗散，避免过多光能对光系统II的伤害，根据上述研究结果，提出了红藻中新的过多能量耗散机制模型。研究成果近期发表在PLOS ONE(2008,3(9):e3134)上。

藻胆体是蓝藻(蓝细菌)和红藻光合作用的主要捕光色素蛋白复合物，由藻胆蛋白和连接蛋白组成，分布于类囊体膜的表面，负责光能的吸收，并主要传递给光系统II，实现光能向化学能的转变。藻胆蛋白和藻胆体的结构与功能的研究，对于阐明光合作用的机制、进化及其在生物医学检测中的应用具有重要的意义。

JBC，2008, 283(50),34946–34953，Lu-Ning Liu，Yu-Zhong Zhang

Watching the Native Supramolecular Architecture of Photosynthetic Membrane in Red Algae

TOPOGRAPHY OF PHYCOBILISOMES AND THEIR CROWDING, DIVERSE DISTRIBUTION PATTERNS*

Lu-Ning Liu, Thijs J. Aartsma, Jean-Claude Thomas?, Gerda E. M. Lamers||, Bai-Cheng Zhou, and Yu-Zhong Zhang1

From the State Key Lab of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Jinan 250100, China, the Department of Biophysics, Huygens Laboratory, Leiden University, Leiden 2300RA, The Netherlands, the ?UMR 8186 CNRS & Ecole Normale Supérieure, Biologie Moléculaire des Organismes Photosynthétiques, Paris F-75230, France, and the ||Institute of Biology, Leiden University, Wassenaarseweg 64, Leiden 2333AL, The Netherlands

The architecture of the entire photosynthetic membrane network determines, at the supramolecular level, the physiological roles of the photosynthetic protein complexes involved. So far, a precise picture of the native configuration of red algal thylakoids is still lacking. In this work, we investigated the supramolecular architectures of phycobilisomes (PBsomes) and native thylakoid membranes from the unicellular red alga Porphyridium cruentum using atomic force microscopy (AFM) and transmission electron microscopy. The topography of single PBsomes was characterized by AFM imaging on both isolated and membrane-combined PBsomes complexes. The native organization of thylakoid membranes presented variable arrangements of PBsomes on the membrane surface. It indicates that different light illuminations during growth allow diverse distribution of PBsomes upon the isolated photosynthetic membranes from P. cruentum, random arrangement or rather ordered arrays, to be observed. Furthermore, the distributions of PBsomes on the membrane surfaces are mostly crowded. This is the first investigation using AFM to visualize the native architecture of PBsomes and their crowding distribution on the thylakoid membrane from P. cruentum. Various distribution patterns of PBsomes under different light conditions indicate the photoadaptation of thylakoid membranes, probably promoting the energy-harvesting efficiency. These results provide important clues on the supramolecular architecture of red algal PBsomes and the diverse organizations of thylakoid membranes in vivo.