The reaction center (RC)−light-harvesting complex 1 (LH1) supercomplex plays a pivotal role in bacterial photosynthesis. Many RC-LH1 complexes integrate an additional protein PufX that is key for bacterial growth and photosynthetic competence. Here, we present a cryo–electron microscopy structure of the RC-LH1-PufX supercomplex from Rhodobacter veldkampii at 2.8-Å resolution. The RC-LH1-PufX monomer contains an LH ring of 15 αβ-polypeptides with a 30-Å gap formed by PufX. PufX acts as a molecular “cross brace” to reinforce the RC-LH1 structure. The unusual PufX-mediated large opening in the LH1 ring and defined arrangement of proteins and cofactors provide the molecular basis for the assembly of a robust RC-LH1-PufX supercomplex and efficient quinone transport and electron transfer. These architectural features represent the natural strategies for anoxygenic photosynthesis and environmental adaptation.

反应中心 (RC)-捕光复合物 1 (LH1) 超复合物在细菌光合作用中起着关键作用。许多 RC-LH1 复合物整合了一种额外的蛋白质 PufX，它是细菌生长和光合作用能力的关键。在这里，我们展示了来自Rhodobacter veldkampii 的 RC-LH1-PufX 超复合物的冷冻电子显微镜结构分辨率为 2.8 Å。RC-LH1-PufX 单体包含一个由 15 个 αβ-多肽组成的 LH 环，由 PufX 形成一个 30-Å 的间隙。PufX 充当分子“交叉支撑”以加强 RC-LH1 结构。LH1 环中不寻常的 PufX 介导的大开口以及蛋白质和辅因子的明确排列为强大的 RC-LH1-PufX 超复合物的组装以及有效的醌转运和电子转移提供了分子基础。这些建筑特征代表了无氧光合作用和环境适应的自然策略。