Bao Han, Burnap Robert L
Department of Microbiology and Molecular Genetics, Oklahoma State University Stillwater, OK, USA.
Front Plant Sci. 2016 May 3;7:578. doi: 10.3389/fpls.2016.00578. eCollection 2016.
Photosynthetic water oxidation is catalyzed by the Mn4CaO5 cluster of photosystem II. The assembly of the Mn4O5Ca requires light and involves a sequential process called photoactivation. This process harnesses the charge-separation of the photochemical reaction center and the coordination environment provided by the amino acid side chains of the protein to oxidize and organize the incoming manganese ions to form the oxo-bridged metal cluster capable of H2O-oxidation. Although most aspects of this assembly process remain poorly understood, recent advances in the elucidation of the crystal structure of the fully assembled cyanobacterial PSII complex help in the interpretation of the rich history of experiments designed to understand this process. Moreover, recent insights on the structure and stability of the constituent ions of the Mn4CaO5 cluster may guide future experiments. Here we consider the literature and suggest possible models of assembly including one involving single Mn(2+) oxidation site for all Mn but requiring ion relocation.
光合水氧化由光系统II的Mn4CaO5簇催化。Mn4O5Ca的组装需要光，且涉及一个称为光激活的连续过程。该过程利用光化学反应中心的电荷分离以及蛋白质氨基酸侧链提供的配位环境来氧化并组织进入的锰离子，以形成能够进行H2O氧化的氧桥连金属簇。尽管该组装过程的大多数方面仍知之甚少，但在阐明完全组装的蓝藻PSII复合物晶体结构方面的最新进展有助于解释为理解该过程而设计的丰富实验历史。此外，对Mn4CaO5簇组成离子的结构和稳定性的最新见解可能会指导未来的实验。在这里，我们考虑相关文献并提出可能的组装模型，其中一个模型涉及所有锰的单一Mn(2+)氧化位点，但需要离子重排。
