Ifuku Kentaro
a Graduate School of Biostudies , Kyoto University , Sakyo-ku, Kyoto , Japan.
Biosci Biotechnol Biochem. 2015;79(8):1223-31. doi: 10.1080/09168451.2015.1031078. Epub 2015 Apr 7.
Photosystem II (PSII), which catalyzes photosynthetic water oxidation, is composed of more than 20 subunits, including membrane-intrinsic and -extrinsic proteins. The extrinsic proteins of PSII shield the catalytic Mn4CaO5 cluster from exogenous reductants and serve to optimize oxygen evolution at physiological ionic conditions. These proteins include PsbO, found in all oxygenic organisms, PsbP and PsbQ, specific to higher plants and green algae, and PsbU, PsbV, CyanoQ, and CyanoP in cyanobacteria. Furthermore, red algal PSII has PsbQ' in addition to PsbO, PsbV, and PsbU, and diatoms have Psb31 in supplement to red algal-type extrinsic proteins, exemplifying the functional divergence of these proteins during evolution. This review provides an updated summary of recent findings on PSII extrinsic proteins and discusses their binding, function, and evolution within various photosynthetic organisms.
光系统II（PSII）催化光合水氧化，由20多个亚基组成，包括膜内在蛋白和外在蛋白。PSII的外在蛋白保护催化性的Mn4CaO5簇免受外源性还原剂的影响，并在生理离子条件下优化氧气释放。这些蛋白包括在所有产氧生物中都存在的PsbO、高等植物和绿藻特有的PsbP和PsbQ，以及蓝细菌中的PsbU、PsbV、CyanoQ和CyanoP。此外，红藻的PSII除了有PsbO、PsbV和PsbU外，还有PsbQ'，硅藻除了有红藻型外在蛋白外，还有Psb31，这例证了这些蛋白在进化过程中的功能差异。本综述提供了关于PSII外在蛋白最新研究结果的总结，并讨论了它们在各种光合生物中的结合、功能和进化。
