Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA.
Science. 2013 Nov 29;342(6162):1104-7. doi: 10.1126/science.1242321.
In photosynthetic organisms, photons are captured by light-harvesting antenna complexes, and energy is transferred to reaction centers where photochemical reactions take place. We describe here the isolation and characterization of a fully functional megacomplex composed of a phycobilisome antenna complex and photosystems I and II from the cyanobacterium Synechocystis PCC 6803. A combination of in vivo protein cross-linking, mass spectrometry, and time-resolved spectroscopy indicates that the megacomplex is organized to facilitate energy transfer but not intercomplex electron transfer, which requires diffusible intermediates and the cytochrome b6f complex. The organization provides a basis for understanding how phycobilisomes transfer excitation energy to reaction centers and how the energy balance of two photosystems is achieved, allowing the organism to adapt to varying ecophysiological conditions.
在光合作用生物中，光子被光捕获天线复合物捕获，能量被转移到反应中心，在那里发生光化学反应。在这里，我们描述了一种完整功能的巨复合物的分离和表征，该复合物由蓝藻集胞藻 PCC 6803 的藻胆体天线复合物和光系统 I 和 II 组成。体内蛋白质交联、质谱和时间分辨光谱的组合表明，该巨复合物的组织方式有利于能量转移，但不利于跨复合物电子转移，后者需要可扩散中间体和细胞色素 b6f 复合物。这种组织为理解藻胆体如何将激发能转移到反应中心以及如何实现两个光系统的能量平衡提供了基础，使生物体能够适应不同的生态生理条件。
