Integration of energy and electron transfer processes in the photosynthetic membrane of Rhodobacter sphaeroides
Integration of energy and electron transfer processes in the photosynthetic membrane of Rhodobacter sphaeroides
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DOI：
10.1016/j.bbabio.2014.02.003
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发表时间：
2014-10-01
影响因子：
4.3
通讯作者：
Hunter, C. Neil
中科院分区：
文献类型：
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作者：
Cartron, Michael L.;Olsen, John D.;Hunter, C. Neil
光合作用将吸收的太阳能转化为质子动力，从而驱动 ATP 合成。使用原子力显微镜 (AFM) 在紫色光养细菌红细菌 (Rba.) sphaeroides 中绘制了负责光吸收、光化学和对苯二酚 (QH(2)) 生产的叶绿素-蛋白质复合物的膜网络，但将 QH2 氧化为醌 (Q) 以产生质子动力的细胞色素 bc(1) (cytbc(1)) 复合物的膜位置尚不清楚。我们用金纳米珠标记了 cytbc(1) 复合物，每个金纳米珠都通过组氨酸 (10) (His(10)) 标签连接到 cytc(1) 的 C 末端。负染色的色素囊泡的电子显微镜 (EM) 显示，大多数 cytbc(1) 复合物以二聚体形式存在于膜中。 cytbc(1) 复合物似乎与反应中心光捕获 1-PufX (RC-LH1-PufX) 复合物相邻，与金标记膜的 AFM 形貌图一致。 His 标记的 cytbc(1) 复合物是从用去垢剂部分溶解的色素细胞中回收的； RC-LH1-PufX 复合物倾向于与 cytbc(1) 共纯化，而 LH2 复合物变得分离，这与靠近 RC-LH1-PufX 阵列的 cytbc(1) 复合物簇一致，但与固定的化学计量 cytbc(1)-RC-LH1-PufX 超复合物不一致。该信息与 RC、cytbc(1)、ATP 合酶、cytaa(3) 和 cytcbb(3) 膜蛋白复合物的定量质谱 (MS) 分析相结合，构建了包含 67 个 LH2 复合物、11 个 LH1-RC-PufX 二聚体和 2 个 RC-LH1-PufX 单体的色素囊泡的原子级模型，4 cytbc(1) 二聚体和 2 个 ATP 合酶。对相互关联的能量、电子和质子转移过程的模拟显示，光强度仅相当于明亮阳光的 1%，ATP 周转率仅为最大的一半。因此，色素细胞的光系统结构针对低光强度下的生长进行了优化。 (C) 2014 Elsevier B.V. 保留所有权利。
Photosynthesis converts absorbed solar energy to a protonmotive force, which drives ATP synthesis. The membrane network of chlorophyll-protein complexes responsible for light absorption, photochemistry and quinol (QH(2)) production has been mapped in the purple phototrophic bacterium Rhodobacter (Rba.) sphaeroides using atomic force microscopy (AFM), but the membrane location of the cytochrome bc(1) (cytbc(1)) complexes that oxidise QH2 to quinone (Q) to generate a protonmotive force is unknown. We labelled cytbc(1) complexes with gold nanobeads, each attached by a Histidine(10) (His(10))-tag to the C-terminus of cytc(1). Electron microscopy (EM) of negatively stained chromatophore vesicles showed that the majority of the cytbc(1), complexes occur as dimers in the membrane. The cytbc(1) complexes appeared to be adjacent to reaction centre light-harvesting 1-PufX (RC-LH1-PufX) complexes, consistent with AFM topographs of a gold-labelled membrane. His-tagged cytbc(1) complexes were retrieved from chromatophores partially solubilised by detergent; RC-LH1-PufX complexes tended to co-purify with cytbc(1) whereas LH2 complexes became detached, consistent with clusters of cytbc(1) complexes close to RC-LH1-PufX arrays, but not with a fixed, stoichiometric cytbc(1)-RC-LH1-PufX supercomplex. This information was combined with a quantitative mass spectrometry (MS) analysis of the RC, cytbc(1), ATP synthase, cytaa(3) and cytcbb(3) membrane protein complexes, to construct an atomic-level model of a chromatophore vesicle comprising 67 LH2 complexes, 11 LH1-RC-PufX dimers & 2 RC-LH1-PufX monomers, 4 cytbc(1) dimers and 2 ATP synthases. Simulation of the interconnected energy, electron and proton transfer processes showed a half-maximal ATP turnover rate for a light intensity equivalent to only 1% of bright sunlight. Thus, the photosystem architecture of the chromatophore is optimised for growth at low light intensities. (C) 2014 Elsevier B.V. All rights reserved.