Iwai Masakazu, Pack Chan-Gi, Takenaka Yoshiko, Sako Yasushi, Nakano Akihiko
1] Live Cell Molecular Imaging Research Team, Extreme Photonics Research Group, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan [2] PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
Sci Rep. 2013 Oct 3;3:2833. doi: 10.1038/srep02833.
Flexibility of chloroplast thylakoid membrane proteins is essential for plant fitness and survival under fluctuating light environments. Phosphorylation of light-harvesting antenna complex II (LHCII) is known to induce dynamic protein reorganization that fine-tunes the rate of energy conversion in each photosystem. However, molecular details of how LHCII phosphorylation causes light energy redistribution throughout thylakoid membranes still remain unclear. By using fluorescence correlation spectroscopy, we here determined the LHCII phosphorylation-dependent protein diffusion in thylakoid membranes isolated from the green alga Chlamydomonas reinhardtii. As compared to the LHCII dephosphorylation-induced condition, the diffusion coefficient of LHCII increased nearly twofold under the LHCII phosphorylation-induced condition. We also verified the results by using the LHCII phosphorylation-deficient mutant. Our observation suggests that LHCII phosphorylation-dependent protein reorganization occurs along with the changes in the rate of protein diffusion, which would have an important role in mediating light energy redistribution throughout thylakoid membranes.
叶绿体类囊体膜蛋白的灵活性对于植物在波动光环境下的适应性和生存至关重要。已知光捕获天线复合物II（LHCII）的磷酸化会诱导动态蛋白质重组，从而微调每个光系统中的能量转换速率。然而，LHCII磷酸化如何导致光能在整个类囊体膜中重新分布的分子细节仍不清楚。通过使用荧光相关光谱法，我们在此确定了从绿藻莱茵衣藻分离的类囊体膜中LHCII磷酸化依赖性蛋白质扩散。与LHCII去磷酸化诱导的条件相比，在LHCII磷酸化诱导的条件下，LHCII的扩散系数增加了近两倍。我们还通过使用LHCII磷酸化缺陷型突变体验证了结果。我们的观察结果表明，LHCII磷酸化依赖性蛋白质重组与蛋白质扩散速率的变化同时发生，这在介导光能在整个类囊体膜中的重新分布中具有重要作用。
