Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Photosynthesis Research Center, Key Laboratory of Photobiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
Biochim Biophys Acta Bioenerg. 2024 Aug 1;1865(3):149050. doi: 10.1016/j.bbabio.2024.149050. Epub 2024 May 27.
Purple phototrophic bacteria possess light-harvesting 1 and reaction center (LH1-RC) core complexes that play a key role in converting solar energy to chemical energy. High-resolution structures of LH1-RC and RC complexes have been intensively studied and have yielded critical insight into the architecture and interactions of their proteins, pigments, and cofactors. Nevertheless, a detailed picture of the structure and assembly of LH1-only complexes is lacking due to the intimate association between LH1 and the RC. To study the intrinsic properties and structure of an LH1-only complex, a genetic system was constructed to express the Thermochromatium (Tch.) tepidum LH1 complex heterologously in a modified Rhodospirillum rubrum mutant strain. The heterologously expressed Tch. tepidum LH1 complex was isolated in a pure form free of the RC and exhibited the characteristic absorption properties of Tch. tepidum. Cryo-EM structures of the LH1-only complexes revealed a closed circular ring consisting of either 14 or 15 αβ-subunits, making it the smallest completely closed LH1 complex discovered thus far. Surprisingly, the Tch. tepidum LH1-only complex displayed even higher thermostability than that of the native LH1-RC complex. These results reveal previously unsuspected plasticity of the LH1 complex, provide new insights into the structure and assembly of the LH1-RC complex, and show how molecular genetics can be exploited to study membrane proteins from phototrophic organisms whose genetic manipulation is not yet possible.
紫色光合细菌拥有光捕获 1 和反应中心 (LH1-RC) 核心复合物，它们在将太阳能转化为化学能方面起着关键作用。LH1-RC 和 RC 复合物的高分辨率结构已经得到了深入研究，并为其蛋白质、色素和辅因子的结构和相互作用提供了关键的见解。然而，由于 LH1 与 RC 之间的密切关联，缺乏对 LH1 仅复合物的结构和组装的详细了解。为了研究 LH1 仅复合物的固有特性和结构，构建了一个遗传系统，以在改良的 Rhodospirillum rubrum 突变株中异源表达 Thermochromatium (Tch.) tepidum LH1 复合物。异源表达的 Tch. tepidum LH1 复合物以纯形式分离，不含 RC，并表现出 Tch. tepidum 的特征吸收特性。LH1 仅复合物的冷冻电镜结构揭示了一个由 14 或 15 个 αβ-亚基组成的闭合环形，使其成为迄今为止发现的最小的完全闭合的 LH1 复合物。令人惊讶的是，Tch. tepidum LH1 仅复合物的热稳定性甚至高于天然 LH1-RC 复合物。这些结果揭示了 LH1 复合物以前未被察觉的可塑性，为 LH1-RC 复合物的结构和组装提供了新的见解，并展示了如何利用分子遗传学来研究那些遗传操作尚未可能的光合生物的膜蛋白。
