Department of Chemistry, University of California, Berkeley, Berkeley, 94720, CA, USA.
Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, 94720, CA, USA.
Nat Commun. 2024 Oct 9;15(1):8763. doi: 10.1038/s41467-024-53138-z.
Photosystem II (PSII) has the unique ability to perform water-splitting. With light-harvesting complexes, it forms the PSII supercomplex (PSII-SC) which is a functional unit that can perform efficient energy conversion, as well as photoprotection, allowing photosynthetic organisms to adapt to the naturally fluctuating sunlight intensity. Achieving these functions requires a collaborative energy transfer network between all subunits of the PSII-SC. In this work, we perform kinetic analyses and characterise the energy landscape of the PSII-SC with a structure-based energy transfer model. With first passage time analyses and kinetic Monte Carlo simulations, we are able to map out the overall energy transfer network. We also investigate how energy transfer pathways are affected when individual protein complexes are removed from the network, revealing the functional roles of the subunits of the PSII-SC. In addition, we provide a quantitative description of the flat energy landscape of the PSII-SC. We show that it is a unique landscape that produces multiple kinetically relevant pathways, corresponding to a high pathway entropy. These design principles are crucial for balancing efficient energy conversion and photoprotection.
光系统 II（PSII）具有独特的水分解能力。它与光捕获复合物一起形成 PSII 超复合体（PSII-SC），这是一个功能单元，可以进行高效的能量转换，以及光保护，使光合作用生物能够适应自然波动的阳光强度。要实现这些功能，需要 PSII-SC 的所有亚基之间的协同能量转移网络。在这项工作中，我们使用基于结构的能量转移模型对 PSII-SC 的动力学进行分析和特征描述。通过首次通过时间分析和动力学蒙特卡罗模拟，我们能够绘制出整体能量转移网络。我们还研究了当从网络中去除单个蛋白质复合物时，能量转移途径如何受到影响，揭示了 PSII-SC 亚基的功能作用。此外，我们还对 PSII-SC 的平坦能量景观进行了定量描述。我们表明，它是一个独特的景观，产生了多个动力学相关的途径，对应于高途径熵。这些设计原则对于平衡高效能量转换和光保护至关重要。
