Assembly and Function of the Photosystem II Manganese Stabilizing Protein

光系统II催化O2释放并提供用于光合作用中糖合成的电子。 O2释放反应由4个Mn原子催化，需要一个关键的蛋白质亚基，锰稳定蛋白，它控制Mn结合和快速O2释放。 该研究项目将表征锰稳定蛋白的结构如何使其在O2进化中发挥作用。 一组实验将确定在N-末端的蛋白质的氨基酸序列，是必不可少的光系统II的结合，也可能需要锰的稳定性和快速O2生产。 第二个研究目标将进一步表征锰稳定蛋白在溶液中的“天然未折叠”行为。 蛋白质的不寻常的热稳定性将被利用作为探针，以扩展其不寻常的溶液结构的表征，并确定在何种程度上的单一-S-S-键可以被证明是必要的锰稳定蛋白质的热稳定性。 相关的实验将确定是否可以证明锰稳定蛋白的某些突变类型的溶液结构变化与它们组装成光系统II相关，以及酶的Mn簇的完整性是否影响这一过程。 第三个研究项目将探索一种高度保守的氨基酸精氨酸的作用，这种氨基酸似乎对锰稳定蛋白促进锰簇催化活性的能力至关重要。 这些实验将与锰稳定蛋白的结构和功能的分析相结合，以发现为什么该氨基酸残基中的其他变化会产生锰稳定蛋白活性的不寻常变化，而蛋白质溶液结构却没有明显变化。

Photosystem II catalyzes O2 evolution and provides electrons that are used for sugar synthesis in photosynthesis. The O2-evolving reaction is catalyzed by 4 Mn atoms and requires a key protein subunit, manganese stabilizing protein, that controls Mn binding and rapid O2 evolution. This research project will characterize how manganese stabilizing protein's structure allows it to perform its role in O2 evolution. One set of experiments will identify amino acid sequences at the N-terminus of the protein that are essential for photosystem II binding, and that may also be required for Mn stability and rapid O2 production. A second research objective will further characterize manganese stabilizing protein's "natively unfolded" behavior in solution. The protein's unusual thermostability will be exploited as a probe to extend the characterization of its unusual solution structure and determine the extent to which the single -S-S- bond can be shown to be necessary for the thermostability of manganese stabilizing protein. Related experiments will determine whether solution structure changes in some mutant types of manganese stabilizing protein can be demonstrated to correlate with their assembly into photosystem II, and whether the integrity of the enzyme's Mn cluster affects this process. A third research project will explore the role of a highly conserved amino acid, arginine, that appears to be essential for manganese stabilizing protein's ability to promote the catalytic activity of the Mn cluster. These experiments will be coupled with analyses of structure and function of manganese stabilizing protein to discover why other changes in this amino acid residue produce unusual changes in manganese stabilizing protein activity without apparent changes in the protein's solution structure.