Structural basis for energy and electron transfer of the photosystem I-IsiA-flavodoxin supercomplex
Structural basis for energy and electron transfer of the photosystem I-IsiA-flavodoxin supercomplex
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光系统I-IsiA-黄素氧还蛋白超复合物能量和电子转移的结构基础
DOI：
10.1038/s41477-020-0593-7
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发表时间：
2020-02-10
期刊：
影响因子：
18
通讯作者：
Li, Mei
中科院分区：
文献类型：
--
作者：
Cao, Peng;Cao, Duanfang;Li, Mei
在缺铁条件下，蓝藻光系统 I 超复合物与铁应激诱导的蛋白质 IsiA 和黄素氧还蛋白结合。它们形成一个高效收集光的网络，并保持正常的电子传输效率。在天然水生环境中经常发生的缺铁胁迫下，蓝藻会减少富铁蛋白的数量，包括光系统 I (PSI) 和铁氧还蛋白 (Fd)，并上调铁胁迫诱导的蛋白 A 和 B（IsiA 和黄素氧还蛋白 (Fld)）的表达。多个IsiAs充当环绕PSI核心的外围天线，而Fld取代Fd作为PSI的电子受体。在这里，我们报道了来自聚球藻的 PSI3-IsiA(18)-Fld(3) 和 PSI3-IsiA(18) 超复合物的结构。 PCC 7942，揭示了与之前报道的 PSI 结构不同的特征，以及涉及之前未观察到的颜料分子的复杂颜料网络。光谱结果表明 IsiAs 是 PSI 的有效光收集器。三个 Fld 对称地结合到三聚 PSI 核心——我们揭示了 PSI 和 Fld 之间的详细相互作用和电子传输路径。我们的研究结果为理解蓝藻 PSI 在应激条件下的光捕获、能量转移和电子传输机制提供了结构基础。
Cyanobacterial photosystem I supercomplexes bind to iron-stress-induced proteins IsiA and flavodoxin under iron-deficiency conditions. They form a network that is highly efficient at light harvesting and retains normal electron transport efficiency.Under iron-deficiency stress, which occurs frequently in natural aquatic environments, cyanobacteria reduce the amount of iron-enriched proteins, including photosystem I (PSI) and ferredoxin (Fd), and upregulate the expression of iron-stress-induced proteins A and B (IsiA and flavodoxin (Fld)). Multiple IsiAs function as the peripheral antennae that encircle the PSI core, whereas Fld replaces Fd as the electron receptor of PSI. Here, we report the structures of the PSI3-IsiA(18)-Fld(3) and PSI3-IsiA(18) supercomplexes from Synechococcus sp. PCC 7942, revealing features that are different from the previously reported PSI structures, and a sophisticated pigment network that involves previously unobserved pigment molecules. Spectroscopic results demonstrated that IsiAs are efficient light harvesters for PSI. Three Flds bind symmetrically to the trimeric PSI core-we reveal the detailed interaction and the electron transport path between PSI and Fld. Our results provide a structural basis for understanding the mechanisms of light harvesting, energy transfer and electron transport of cyanobacterial PSI under stressed conditions.