Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ 85287-5001, USA.
School of Molecular Sciences, Arizona State University, Tempe, AZ 85287-1604, USA.
Sci Adv. 2020 Feb 5;6(6):eaay6415. doi: 10.1126/sciadv.aay6415. eCollection 2020 Feb.
Phototrophic organisms are superbly adapted to different light environments but often must acclimate to challenging competition for visible light wavelengths in their niches. Some cyanobacteria overcome this challenge by expressing paralogous photosynthetic proteins and by synthesizing and incorporating ~8% chlorophyll f into their Photosystem I (PSI) complexes, enabling them to grow under far-red light (FRL). We solved the structure of FRL-acclimated PSI from the cyanobacterium PCC 7521 by single-particle, cryo-electron microscopy to understand its structural and functional differences. Four binding sites occupied by chlorophyll f are proposed. Subtle structural changes enable FRL-adapted PSI to extend light utilization for oxygenic photosynthesis to nearly 800 nm. This structure provides a platform for understanding FRL-driven photosynthesis and illustrates the robustness of adaptive and acclimation mechanisms in nature.
光能自养生物非常适应不同的光照环境，但在其生境中，往往必须适应对可见波长光的激烈竞争。一些蓝细菌通过表达同源光合蛋白，并合成和掺入约 8%叶绿素 f 到它们的光系统 I（PSI）复合物来克服这一挑战，使它们能够在远红（FRL）光下生长。我们通过单颗粒低温电子显微镜解析了来自蓝细菌 PCC 7521 的 FRL 适应 PSI 的结构，以了解其结构和功能差异。提出了四个叶绿素 f 占据的结合位点。细微的结构变化使 FRL 适应 PSI 将氧气光合作用的光利用扩展到近 800nm。该结构为理解 FRL 驱动的光合作用提供了一个平台，并说明了自然中适应和适应机制的稳健性。
