The reaction centre light-harvesting 1 (RC–LH1) complex is the core functional component of bacterial photosynthesis. We determined the cryo-electron microscopy (cryo-EM) structure of the RC–LH1 complex from Rhodospirillum rubrum at 2.5 Å resolution, which reveals a unique monomeric bacteriochlorophyll with a phospholipid ligand in the gap between the RC and LH1 complexes. The LH1 complex comprises a circular array of 16 αβ-polypeptide subunits that completely surrounds the RC, with a preferential binding site for a quinone, designated QP, on the inner face of the encircling LH1 complex. Quinols, initially generated at the RC QB site, are proposed to transiently occupy the QP site prior to traversing the LH1 barrier and diffusing to the cytochrome bc1 complex. Thus, the QP site, which is analogous to other such sites in recent cryo-EM structures of RC–LH1 complexes, likely reflects a general mechanism for exporting quinols from the RC–LH1 complex.

中文翻译：

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2.5 Å 处红色红螺菌 RC-LH1 复合物的冷冻电镜结构

反应中心捕光 1 (RC-LH1) 复合物是细菌光合作用的核心功能成分。我们以 2.5 Å 的分辨率确定了来自红色红螺菌的 RC-LH1 复合物的冷冻电子显微镜 (cryo-EM) 结构，这揭示了一种独特的单体细菌叶绿素，在 RC 和 LH1 复合物之间的间隙中带有磷脂配体。LH1 复合物包含 16 个 αβ-多肽亚基的圆形阵列，完全围绕着 RC，在环绕的 LH1 复合物的内表面上有一个醌优先结合位点，称为 QP。喹诺醇最初在 RC QB 位点产生，被提议在穿过 LH1 屏障并扩散到细胞色素 bc1 复合物之前暂时占据 QP 位点。因此，QP网站，