Fehr Niklas, Dietz Carsten, Polyhach Yevhen, von Hagens Tona, Jeschke Gunnar, Paulsen Harald
From the Department of General Botany, Johannes Gutenberg-University, 55128 Mainz, Germany and.
the Department of Physical Chemistry, ETH Zürich, Vladimir Prelog-Weg 2, CH-8093 Zürich, Switzerland.
J Biol Chem. 2015 Oct 23;290(43):26007-20. doi: 10.1074/jbc.M115.669804. Epub 2015 Aug 27.
The major light harvesting complex II (LHCII) of green plants plays a key role in the absorption of sunlight, the regulation of photosynthesis, and in preventing photodamage by excess light. The latter two functions are thought to involve the lumenal loop and the N-terminal domain. Their structure and mobility in an aqueous environment are only partially known. Electron paramagnetic resonance (EPR) has been used to measure the structure of these hydrophilic protein domains in detergent-solubilized LHCII. A new technique is introduced to prepare LHCII trimers in which only one monomer is spin-labeled. These heterogeneous trimers allow to measure intra-molecular distances within one LHCII monomer in the context of a trimer by using double electron-electron resonance (DEER). These data together with data from electron spin echo envelope modulation (ESEEM) allowed to model the N-terminal protein section, which has not been resolved in current crystal structures, and the lumenal loop domain. The N-terminal domain covers only a restricted area above the superhelix in LHCII, which is consistent with the "Velcro" hypothesis to explain thylakoid grana stacking (Standfuss, J., van Terwisscha Scheltinga, A. C., Lamborghini, M., and Kühlbrandt, W. (2005) EMBO J. 24, 919-928). The conformation of the lumenal loop domain is surprisingly different between LHCII monomers and trimers but not between complexes with and without neoxanthin bound.
绿色植物的主要捕光复合物II（LHCII）在太阳光吸收、光合作用调节以及防止过量光照造成的光损伤方面发挥着关键作用。后两项功能被认为涉及腔环和N端结构域。它们在水性环境中的结构和流动性仅部分为人所知。电子顺磁共振（EPR）已被用于测量去污剂溶解的LHCII中这些亲水性蛋白质结构域的结构。引入了一种新技术来制备仅一个单体被自旋标记的LHCII三聚体。这些异质三聚体能够通过使用双电子-电子共振（DEER）在三聚体的背景下测量一个LHCII单体内部的分子内距离。这些数据与来自电子自旋回波包络调制（ESEEM）的数据一起，使得能够对N端蛋白质部分和腔环结构域进行建模，而这在当前的晶体结构中尚未得到解析。N端结构域仅覆盖LHCII中超螺旋上方的一个受限区域，这与解释类囊体基粒堆叠的“维可牢”假说一致（Standfuss, J., van Terwisscha Scheltinga, A. C., Lamborghini, M., and Kühlbrandt, W. (2005) EMBO J. 24, 919 - 928）。腔环结构域的构象在LHCII单体和三聚体之间惊人地不同，但在结合和未结合新黄质的复合物之间没有差异。
