Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 200125, Shanghai, China.
Shanghai Institute of Precision Medicine, 200125, Shanghai, China.
Nat Commun. 2020 Feb 14;11(1):888. doi: 10.1038/s41467-020-14732-z.
NDH-1 is a key component of the cyclic-electron-transfer around photosystem I (PSI CET) pathway, an important antioxidant mechanism for efficient photosynthesis. Here, we report a 3.2-Å-resolution cryo-EM structure of the ferredoxin (Fd)-NDH-1L complex from the cyanobacterium Thermosynechococcus elongatus. The structure reveals three β-carotene and fifteen lipid molecules in the membrane arm of NDH-1L. Regulatory oxygenic photosynthesis-specific (OPS) subunits NdhV, NdhS and NdhO are close to the Fd-binding site whilst NdhL is adjacent to the plastoquinone (PQ) cavity, and they play different roles in PSI CET under high-light stress. NdhV assists in the binding of Fd to NDH-1L and accelerates PSI CET in response to short-term high-light exposure. In contrast, prolonged high-light irradiation switches on the expression and assembly of the NDH-1MS complex, which likely contains no NdhO to further accelerate PSI CET and reduce ROS production. We propose that this hierarchical mechanism is necessary for the survival of cyanobacteria in an aerobic environment.
NDH-1 是光合作用中循环电子传递（PSI CET）途径的关键组成部分，也是一种有效的抗氧化机制。在这里，我们报告了来自嗜热栖热菌的铁氧还蛋白（Fd）-NDH-1L 复合物的 3.2Å 分辨率冷冻电镜结构。该结构揭示了 NDH-1L 膜臂中的三个β-胡萝卜素和十五个脂质分子。调节放氧光合作用特异性（OPS）亚基 NdhV、NdhS 和 NdhO 靠近 Fd 结合位点，而 NdhL 则靠近质体醌（PQ）腔，它们在高光胁迫下的 PSI CET 中发挥不同的作用。NdhV 有助于 Fd 与 NDH-1L 的结合，并在短期高光暴露下加速 PSI CET。相比之下，长时间的高光照射会激活 NDH-1MS 复合物的表达和组装，该复合物可能不含 NdhO，以进一步加速 PSI CET 并减少 ROS 产生。我们提出，这种层次化的机制对于需氧环境中蓝藻的生存是必要的。
