Collaborative Research: Structural and Molecular Mechanisms for Protein Repair in Photosynthetic Membranes

在我们对光合作用的理解中，一个重要的知识空白是植物如何能够修复光系统II（PSII），即捕获光能的多蛋白质全复合物。 本项目的目的是确定PSII的磷酸化改变类囊体超微结构的机制，使受损的PSII被有效地动员从密集堆积的基粒膜未堆积的类囊体膜，它可以修复回收。 核心假设是PSII磷酸化引发基质侧的基粒直径减小和相邻基粒膜分离，从而促进受损PSII的运动。此外，据推测，蛋白质磷酸化增加PSII流动性触发拆除的大规模holocomplex和产生静电排斥。 提出的研究的基本原理是，一旦蛋白质磷酸化调节PSII流动性的机制是已知的，一个更好的基本理解是植物如何保持其光合机制的最佳生长和发育。通过追求两个具体目标来检验中心假设。目的1：用冷冻电镜观察类囊体超微结构磷酸化特异性变化。目的2：确定揭示磷酸化如何动员PSII在基粒中的分子机制。该方法是测量扩散数据的荧光恢复后光漂白（FRAP）在不同的修复条件下，然后将这些结果进行比较的FRAP模型开发的Monte Carlo模拟。这些办法将产生以下预期成果。成果1：预期蛋白磷酸化诱导基粒直径减小，相邻基粒盘之间的距离变大。这两种超微结构的变化都有利于受损的PSII迁移到基质层。结果2：预期磷酸化通过解体和静电排斥加速受损PSII的侧向扩散。这些结果预计将产生一个深入的了解PSII降解的机制，以及为什么蛋白质磷酸化是必需的动员受损的基粒托管PSII。 更广泛的影响这项研究对理解许多其他生物膜中的分子动力学具有更广泛的影响，因为潜在的机制可能是相似的。该项目的社会效益是，更好地了解植物如何维持其光合作用机制将有助于提高农作物在粮食和生物燃料前景方面的稳健性和效率。该项目为两名本科生提供了光合作用研究领域的培训机会。 将努力让来自科学领域代表性不足群体的本科生填补这些职位。 该项目将利用计算机电影的强烈直观性，生成一个基于计算机的教学平台。专题课程将开发为一个新的基于互联网的课程，题为“分子在运动。“华盛顿州立大学的研究生以及世界各地的其他人都可以参加这门课程

Intellectual Merit An essential gap of knowledge in our understanding of photosynthesis is how are plants able to repair photosystem II (PSII), the multi-protein holocomplex which captures light energy. The objective of this project is to determine the mechanisms by which phosphorylation of PSII alters the thylakoid ultrastructure and enables damaged PSII to be efficiently mobilized from densely packed stacked grana membranes to unstacked thylakoid membranes where it can be repaired for recycling. The central hypothesis is that PSII phosphorylation triggers a reduction in the grana diameter and separation of adjacent grana membranes on the stromal side thereby facilitating the movement of damaged PSII. Furthermore it is hypothesized that protein phosphorylation increases PSII mobility by triggering the dismantling of the massive holocomplex and by generating electrostatic repulsion. The rationale of the proposed research is that, once the mechanisms by which protein phosphorylation regulates PSII mobility are known, a better fundamental understanding is available of how plants maintain their photosynthetic machinery for optimal growth and development. The central hypothesis is tested by pursuing two specific aims. Aim 1: Determine phosphorylation-specific changes in the thylakoid ultrastructure by cryo-electron microscopy. Aim 2: Determine the molecular mechanisms revealing how phosphorylation mobilizes PSII in grana. The approach is to measure diffusion data by fluorescence-recovery after photobleaching (FRAP) under various repair conditions and then to compare these results to a FRAP model developed by Monte Carlo-simulations. These approaches will lead to the following expected outcomes. Outcome 1: It is expect that protein-phosphorylation induces a reduction of the grana diameter and that the distance between adjacent grana discs becomes larger. Both ultrastructural changes would facilitate migration of damaged PSII to reach stroma lamellae. Outcome 2: It is expect that phosphorylation accelerates lateral diffusion of damaged PSII by disassembly and electrostatic repulsion. These results are expected to yield an in-depth understanding on the mechanisms of the PSII degradation and also why protein phosphorylation is required for mobilization of damaged grana-hosted PSII. Broader Impact This research has a broader impact for the understanding of the molecular dynamics in many other biomembranes since the underlying mechanisms are likely to be similar. The societal benefit of the project is that a better understanding of how plants maintain their photosynthetic machinery will help to increase the robustness and efficiency of crop plants for food and biofuel prospects. The project provides training opportunities for two undergraduate students in the exciting field of photosynthesis research. Efforts will be made to fill these positions by undergraduates from groups under-represented in the sciences. The project will take advantage of the strong intuitive character of computer movies to generate a computer-based teaching platform. Special topics courses will be developed as a new internet-based course entitled "Molecules in Motion." This course will be accessible to graduate students of Washington State University as well as to others throughout the world