Kimura Yukihiro, Kanno Ryo, Mori Kaisei, Matsuda Yoshiki, Seto Ryuta, Takenaka Shinji, Mino Hiroyuki, Ohkubo Tatsunari, Honda Mai, Sasaki Yuji C, Kishikawa Jun-Ichi, Mitsuoka Kaoru, Mio Kazuhiro, Hall Malgorzata, Purba Endang R, Mochizuki Toshiaki, Mizoguchi Akira, Humbel Bruno M, Madigan Michael T, Wang-Otomo Zheng-Yu, Tani Kazutoshi
Department of Agrobioscience, Graduate School of Agriculture, Kobe University, Kobe, Nada 657-8501, Japan.
Quatum Wave Microscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Kunigami-gun, Okinawa 904-0495, Japan.
Biochemistry. 2025 Jan 7;64(1):170-179. doi: 10.1021/acs.biochem.4c00506. Epub 2024 Dec 16.
is a hot spring purple nonsulfur phototrophic bacterium that contains bacteriochlorophyll (BChl) . Here, we present a 2.21 Å cryo-EM structure of the thermostable light-harvesting 1-reaction center (LH1-RC) complex from . The LH1 ring comprises 16 circularly arranged αβγ-subunits plus one αβ-subunit that surround the RC complex composed of C-, H-, L-, and M-subunits. In a comparative study, the LH1-RC showed numerous electrostatic and hydrophobic interactions both within the LH1 complex itself and between the LH1 and the RC complexes that are absent from the LH1-RC complex of its mesophilic counterpart, . These additional interactions result in a tightly packed LH1-RC architecture with a reduced accessible surface area per volume that enhances the thermal stability of the complex and allows the light reactions of photosynthesis to proceed at hot spring temperatures. Moreover, based on high-resolution structural information combined with spectroscopic evidence, the unique photosynthetic property of the LH1-RC─absorption of energy-poor near-infrared light beyond 1000 nm─can be attributed to strong hydrogen-bonding interactions between the C3-acetyl C═O of the LH1 BChl and two LH1 α-Trp residues, structural rigidity of the LH1, and the enhanced exciton coupling of the LH1 BChls of this thermophile.
是一种含有细菌叶绿素（BChl）的温泉紫色非硫光合细菌。在此，我们展示了来自该细菌的热稳定光捕获1 - 反应中心（LH1 - RC）复合物的2.21 Å冷冻电镜结构。LH1环由16个呈圆形排列的αβγ亚基加上一个αβ亚基组成，它们围绕着由C、H、L和M亚基组成的RC复合物。在一项比较研究中，该LH1 - RC在LH1复合物自身内部以及LH1与RC复合物之间显示出许多静电和疏水相互作用，而其嗜温对应物的LH1 - RC复合物中则不存在这些相互作用。这些额外的相互作用导致形成紧密堆积的LH1 - RC结构，每单位体积的可及表面积减小，这增强了复合物的热稳定性，并使光合作用的光反应能够在温泉温度下进行。此外，基于高分辨率结构信息并结合光谱证据，该LH1 - RC独特的光合特性——吸收超过1000 nm的能量较低的近红外光——可归因于LH1 BChl 的C3 - 乙酰基C═O与两个LH1 α - 色氨酸残基之间的强氢键相互作用、LH1的结构刚性以及该嗜热菌LH1 BChls增强的激子耦合。
