Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, UK.
Electron Bio-imaging Centre, Diamond Light Source, Didcot, UK.
Nature. 2018 Apr;556(7700):203-208. doi: 10.1038/s41586-018-0014-5. Epub 2018 Apr 4.
The light-harvesting 1-reaction centre (LH1-RC) complex is a key functional component of bacterial photosynthesis. Here we present a 2.9 Å resolution cryo-electron microscopy structure of the bacteriochlorophyll b-based LH1-RC complex from Blastochloris viridis that reveals the structural basis for absorption of infrared light and the molecular mechanism of quinone migration across the LH1 complex. The triple-ring LH1 complex comprises a circular array of 17 β-polypeptides sandwiched between 17 α- and 16 γ-polypeptides. Tight packing of the γ-apoproteins between β-polypeptides collectively interlocks and stabilizes the LH1 structure; this, together with the short Mg-Mg distances of bacteriochlorophyll b pairs, contributes to the large redshift of bacteriochlorophyll b absorption. The 'missing' 17th γ-polypeptide creates a pore in the LH1 ring, and an adjacent binding pocket provides a folding template for a quinone, Q , which adopts a compact, export-ready conformation before passage through the pore and eventual diffusion to the cytochrome bc complex.
集光 1 反应中心（LH1-RC）复合物是细菌光合作用的关键功能组件。在这里，我们呈现了来自绿硫菌的基于细菌叶绿素 b 的 LH1-RC 复合物的 2.9 Å 分辨率冷冻电子显微镜结构，揭示了吸收红外光的结构基础和醌类在 LH1 复合物中迁移的分子机制。三重环 LH1 复合物由 17 个β-多肽夹在 17 个α-和 16 个γ-多肽之间的圆形阵列组成。γ-脱辅基蛋白在β-多肽之间的紧密包装共同锁定和稳定 LH1 结构；这与细菌叶绿素 b 对的短 Mg-Mg 距离一起，导致细菌叶绿素 b 吸收的红移较大。“缺失”的第 17 个γ-多肽在 LH1 环中形成一个孔，相邻的结合口袋为醌 Q 提供了一个折叠模板，Q 在通过孔并最终扩散到细胞色素 bc 复合物之前，采用紧凑的、准备出口的构象。
