Photosystem Two accessory proteins: structures binding sites and functions

光系统两种辅助蛋白：结构结合位点和功能

• 批准号: BB/I00937X/1
• 负责人: Peter Nixon
• 金额: $ 65.24万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FI00937X%2F1
• 关键词: Photosystem; Two; accessory; proteins; structures

The Photosystem Two (PSII) complex has quite rightly been described as the 'Engine of Life'. This molecular machine which is found in plants, algae and cyanobacteria is able to use the energy of sunlight to split very stable and abundant water molecules into molecular oxygen, which is released into the atmosphere as a by-product, protons which are used to generate ATP, and 'high energy' electrons which are ultimately used with the ATP to fix atmospheric carbon dioxide into sugar molecules. These carbohydrates can then be used as a fuel and to synthesise biomass for growth. Over the years there has been considerable effort to understand the structure of PSII and how it works. It is now known that PSII is made up of over 20 individual proteins, bound together as a large protein complex in a lipid membrane. Tightly associated with this complex are pigments that harvest the solar energy, small organic molecules that can transport high-energy electrons and a metal cluster comprising one calcium and 4 manganese ions. It is at this metal cluster, buried deep in the protein complex, that water binds and is oxidised to molecular oxygen, giving up its electrons. But PSII is not a perfect machine; it sometimes breaks down, especially when the sunlight is very bright, and has to be repaired. To do this the damaged PSII complex is partially disassembled into a smaller complex, and the damaged protein is recognised, specifically degraded by special proteases found within the membrane, a new protein inserted and the complex reassembled. Without this special repair mechanism PSII would be quickly inactivated in the light and plant growth and oxygen evolution would be inhibited. The purpose of our research is to understand how PSII functions, how PSII is assembled from its component parts and how it is repaired efficiently. Understanding these processes might allow us in the future to enhance photosynthesis in crop plants so that we can increase growth to help satisfy the ever increasing demand for more food and more biomass. This knowledge might also have applications in the design of new, sustainable herbicides or the design of new man-made catalysts that might act as 'artificial leaves' to provide renewable fuels from solar energy. Previous work has identified a number of small proteins that seem to be involved in the assembly, repair or optimal functioning of PSII. We propose to determine the structures of these 'accessory' proteins, so we can see how they are folded in space, and how they bind with PSII. To help do this we have made large amounts of our target proteins in a bacterium, purified the proteins and made crystals which we can use in X-ray diffraction experiments to determine the structure. Alternatively we can also use nuclear magnetic resonance (NMR) spectroscopy which has the advantage that crystals need not be made. We have also been able to make complexes between some of the accessory proteins and either the intact oxygen-evolving PSII complex or smaller protein segments. Analysis of these complexes by x-ray crystallography or NMR will allow us, for the first time, to observe how these accessory proteins engage with PSII at the molecular level. It is important to relate these structural interactions with what is happening in the cell. To do this we have made strains of a cyanobacterium that lack these accessory proteins. By studying PSII assembly and repair and PSII activity in these strains we hope to be able to identify a precise defect in PSII that can be related to the structural results. In this way we will be able learn valuable new information on how the 'Engine of Life' is assembled and maintained in a working state.

第二光系统（PSII）复合体被正确地描述为“生命引擎”。这种存在于植物、藻类和蓝细菌中的分子机器能够利用阳光的能量将非常稳定和丰富的水分子分解成分子氧，分子氧作为副产品释放到大气中，质子用于产生ATP 和“高能”电子最终与 ATP 一起将大气中的二氧化碳固定为糖分子。这些碳水化合物随后可用作燃料并合成用于生长的生物质。多年来，人们为了解 PSII 的结构及其工作原理付出了巨大的努力。现在已知 PSII 由 20 多种单独的蛋白质组成，这些蛋白质在脂膜上结合在一起形成一个大的蛋白质复合物。与这种复合物紧密相关的是收集太阳能的颜料、可以传输高能电子的有机小分子以及包含 1 个钙离子和 4 个锰离子的金属簇。正是在这个深埋在蛋白质复合物中的金属簇中，水与水结合并被氧化成分子氧，释放出电子。但 PSII 并不是一台完美的机器；它有时会发生故障，尤其是在阳光非常明亮的情况下，必须进行修复。为此，受损的 PSII 复合物被部分分解成更小的复合物，受损的蛋白质被识别，并被膜内发现的特殊蛋白酶特异性降解，插入新的蛋白质并重新组装复合物。如果没有这种特殊的修复机制，PSII 将在光照下迅速失活，植物生长和氧气释放将受到抑制。我们研究的目的是了解 PSII 的功能、PSII 的组成部分如何组装以及如何有效修复。了解这些过程可能使我们在未来能够增强农作物的光合作用，从而促进生长，帮助满足对更多食物和更多生物质不断增长的需求。这些知识也可能应用于新型可持续除草剂的设计，或新型人造催化剂的设计，这些催化剂可以充当“人造叶子”，利用太阳能提供可再生燃料。之前的工作已经鉴定出许多小蛋白质，它们似乎参与 PSII 的组装、修复或最佳功能。我们建议确定这些“辅助”蛋白质的结构，这样我们就可以看到它们如何在空间中折叠，以及它们如何与 PSII 结合。为了帮助实现这一目标，我们在细菌中制备了大量的目标蛋白，纯化了这些蛋白并制备了晶体，我们可以在 X 射线衍射实验中使用这些晶体来确定其结构。或者，我们也可以使用核磁共振（NMR）光谱，其优点是无需制造晶体。我们还能够在一些辅助蛋白与完整的释氧 PSII 复合物或更小的蛋白片段之间形成复合物。通过 X 射线晶体学或 NMR 对这些复合物进行分析将使我们首次能够观察这些辅助蛋白如何在分子水平上与 PSII 结合。将这些结构相互作用与细胞中发生的事情联系起来非常重要。为此，我们培育了缺乏这些辅助蛋白的蓝藻菌株。通过研究这些菌株中的 PSII 组装和修复以及 PSII 活性，我们希望能够识别出与结构结果相关的 PSII 中的精确缺陷。通过这种方式，我们将能够了解有关“生命引擎”如何组装并保持在工作状态的宝贵新信息。

项目成果

The Psb27 assembly factor binds to the CP43 complex of photosystem II in the cyanobacterium Synechocystis sp. PCC 6803.

Psb27 组装因子与蓝藻集胞藻属光系统 II 的 CP43 复合物结合。

• DOI: http://dx.10.1104/pp.111.184184
• 发表时间: 2012
• 期刊: Plant physiology
• 影响因子: 7.4
• 作者: Komenda J

Crystal structure of the Psb28 accessory factor of Thermosynechococcus elongatus photosystem II at 2.3 Å.

细长热聚球藻光系统 II 的 Psb28 辅助因子的晶体结构，2.3 ×。

• DOI: http://dx.10.1007/s11120-013-9939-6
• 发表时间: 2013
• 期刊: Photosynthesis research
• 影响因子: 3.7
• 作者: Bialek W

Assembling and maintaining the Photosystem II complex in chloroplasts and cyanobacteria.

在叶绿体和蓝细菌中组装和维持光系统 II 复合体。

• DOI: 10.1016/j.pbi.2012.01.017
• 发表时间: 2012-06-01
• 期刊: Current opinion in plant biology
• 影响因子: 9.5
• 作者: J. Komenda;R. Sobotka;P. Nixon
• 通讯作者: P. Nixon

CyanoP is Involved in the Early Steps of Photosystem II Assembly in the Cyanobacterium Synechocystis sp. PCC 6803.

CyanoP 参与蓝藻集胞藻中光系统 II 组装的早期步骤。

• DOI: http://dx.10.1093/pcp/pcw115
• 发表时间: 2016
• 期刊: Plant & cell physiology
• 影响因子: 4.9
• 作者: Knoppová J

A reaction center-dependent photoprotection mechanism in a highly robust photosystem II from an extremophilic red alga, Cyanidioschyzon merolae.

来自极端极端红藻 Cyanidioschyzon merolae 的高度稳健的光系统 II 中的反应中心依赖性光保护机制。

• DOI: http://dx.10.1074/jbc.m113.484659
• 发表时间: 2013
• 期刊: The Journal of biological chemistry
• 作者: Krupnik T