Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.
Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.
Biochim Biophys Acta Bioenerg. 2017 Oct;1858(10):815-822. doi: 10.1016/j.bbabio.2017.07.003. Epub 2017 Aug 2.
In the first step of the photosynthetic process, light is absorbed by the pigments associated with the antenna proteins, known as light-harvesting complexes (Lhcs), which in vivo are functionally organized as hetero-oligomers. The architecture of the pigments, chlorophylls, and carotenoids bound to each LHC is responsible for the efficient excitation energy transfer resulting in photochemistry. So far, the only LHC studied in depth was LHCII, the most abundant membrane protein of plants, while less information was available for the other antennae. In particular, despite the availability of the structure of CP29 obtained at near atomic resolution in 2011 (Pan et al., 2011), the mismatch in pigment content and spectroscopic properties between CP29 in solution and in the crystal has hampered the possibility to use the structure to interpret the experimental data. In this work, we purified CP29 and its larger assembly (CP29-LHCII-CP24) from the membrane in very mild conditions using a His-tag, and we have studied their pigment binding and spectroscopic properties. In addition, we have performed mutation analysis in vivo to obtain mutants of CP29 lacking individual chlorophylls. The peculiar properties of this antenna support its role in directing the energy flow from the external antennae to the reaction center.
在光合作用的第一步中，光被与天线蛋白相关的色素吸收，这些色素被称为光捕获复合物（Lhcs），在体内它们以异源寡聚体的形式进行功能组织。结合到每个 LHC 的色素、叶绿素和类胡萝卜素的结构负责有效的激发能量转移，从而导致光化学。到目前为止，唯一深入研究的 LHC 是 LHCII，它是植物中最丰富的膜蛋白，而其他天线的信息较少。特别是，尽管 2011 年已经获得了近原子分辨率的 CP29 结构（Pan 等人，2011 年），但溶液中的 CP29 和晶体中的 CP29 在色素含量和光谱性质上的不匹配阻碍了利用结构来解释实验数据的可能性。在这项工作中，我们使用 His 标签在非常温和的条件下从膜中纯化 CP29 及其较大的组装体（CP29-LHCII-CP24），并研究了它们的色素结合和光谱性质。此外，我们还进行了体内突变分析，以获得缺少单个叶绿素的 CP29 突变体。这个天线的特殊性质支持它在将能量从外部天线引导到反应中心的作用。
