Structure of a monomeric photosystem II core complex from a cyanobacterium acclimated to far-red light reveals the functions of chlorophylls d and f.
Structure of a monomeric photosystem II core complex from a cyanobacterium acclimated to far-red light reveals the functions of chlorophylls d and f.
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DOI：
10.1016/j.jbc.2021.101424
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发表时间：
2022-01
期刊：
影响因子：
--
通讯作者：
Bryant DA
中科院分区：
文献类型：
--
作者：
Gisriel CJ;Shen G;Ho MY;Kurashov V;Flesher DA;Wang J;Armstrong WH;Golbeck JH;Gunner MR;Vinyard DJ;Debus RJ;Brudvig GW;Bryant DA
蓝细菌的远红光（FRL）光驯化通过将光合有效辐射的范围扩大到包括远红光/近红外光（700-800 nm）而为一些陆生蓝细菌提供选择性生长优势。在这个光适应过程中，光系统II（PSII），水：质体醌光氧化还原酶参与产氧光合作用，被修改。所得到的FRL-PSII由FRL特异性核心亚基组成，并结合叶绿素（Chl）d和Chl f分子，代替细胞在可见光下生长时发现的几种Chl a分子。这些新的叶绿素有效地降低了能量，规范上认为定义了驱动水氧化的光化学催化所需的光的“红色极限”。FRL-PSII结构的变化以前是未知的，Chl d和Chl f分子的位置仅从间接证据中提出。在这里，我们描述了2.25 μ m分辨率的冷冻电镜结构的单体FRL-PSII核心复合物从聚球藻属PCC 7335细胞，适应FRL。我们确定了一个叶绿素d分子在ChlD 1的电子转移链的位置和四个叶绿素f分子的核心天线。我们还提出意见，提高我们的理解PSII的生物合成，特别是在受体侧的复杂的碳酸氢盐分子被替换的谷氨酸侧链的情况下的组装因子PSB 28。总之，这些结果为驱动水氧化所需的能量下限提供了结构基础，这是地球上大多数太阳能利用的途径。
Far-red light (FRL) photoacclimation in cyanobacteria provides a selective growth advantage for some terrestrial cyanobacteria by expanding the range of photosynthetically active radiation to include far-red/near-infrared light (700–800 nm). During this photoacclimation process, photosystem II (PSII), the water:plastoquinone photooxidoreductase involved in oxygenic photosynthesis, is modified. The resulting FRL-PSII is comprised of FRL-specific core subunits and binds chlorophyll (Chl) d and Chl f molecules in place of several of the Chl a molecules found when cells are grown in visible light. These new Chls effectively lower the energy canonically thought to define the “red limit” for light required to drive photochemical catalysis of water oxidation. Changes to the architecture of FRL-PSII were previously unknown, and the positions of Chl d and Chl f molecules had only been proposed from indirect evidence. Here, we describe the 2.25 Å resolution cryo-EM structure of a monomeric FRL-PSII core complex from Synechococcus sp. PCC 7335 cells that were acclimated to FRL. We identify one Chl d molecule in the ChlD1 position of the electron transfer chain and four Chl f molecules in the core antenna. We also make observations that enhance our understanding of PSII biogenesis, especially on the acceptor side of the complex where a bicarbonate molecule is replaced by a glutamate side chain in the absence of the assembly factor Psb28. In conclusion, these results provide a structural basis for the lower energy limit required to drive water oxidation, which is the gateway for most solar energy utilization on earth.
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