The PsbQ protein defines cyanobacterial Photosystem II complexes with highest activity and stability
The PsbQ protein defines cyanobacterial Photosystem II complexes with highest activity and stability
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DOI：
10.1073/pnas.0609337104
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发表时间：
2007-02-13
影响因子：
11.1
通讯作者：
Pakrasi, Himadri B.
中科院分区：
文献类型：
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作者：
Roose, Johnna L.;Kashino, Yasuhiro;Pakrasi, Himadri B.
光系统11(PSII)光诱导水转化为分子氧是生物圈中最重要的酶反应之一。PSII是一种多亚单位膜蛋白复合体，具有许多相关的辅因子，但由于其正常的功能，由于其频繁的光介导的损伤，它不断地经历组装和拆解。因此，在任何时刻，细胞内PSII复合体的亚基组成都存在异质性。特别是，蓝藻PSII复合体有五个相关的外源蛋白，PsbO，PSBP，PsbQ，PsbU和PsbV。然而，人们对最近发现的PsbQ蛋白与蓝藻PSII中其他成分的相互作用知之甚少。在这里，我们证明了PSII复合体可以从蓝藻集胞藻中分离出来。在多组氨酸标记的PsbQ蛋白存在的基础上，对PCC6803进行了鉴定。用标记的外源蛋白纯化PSII复合体以前没有描述过，这项工作最终证明PsbQ与PsbO、PsbL1和PsbV蛋白一起存在于蓝藻PSII中。此外，与组氨酸标记的完整膜蛋白CP47相比，PsbQ相关的PSII复合体具有更高的活性和稳定性。因此，我们得出结论，PsbQ的存在定义了该酶的完全组装和最佳活性形式。
Light-induced conversion of water to molecular oxygen by Photosystem 11 (PSII) is one of the most important enzymatic reactions in the biosphere. PSII is a multisubunit membrane protein complex with numerous associated cofactors, but it continually undergoes assembly and disassembly due to frequent light-mediated damage as a result of its normal function. Thus, at any instant, there is heterogeneity in the subunit compositions of PSII complexes within the cell. In particular, cyanobacterial PSII complexes have five associated extrinsic proteins, PsbO, PsbP, PsbQ, PsbU, and PsbV. However, little is known about the interactions of the more recently identified PsbQ protein with other components in cyanobacterial PSII. Here we show that PSII complexes can be isolated from the cyanobacterium Synechocystis sp. PCC 6803 on the basis of the presence of a polyhistidine-tagged PsbQ protein. Purification of PSII complexes using a tagged extrinsic protein has not been previously described, and this work conclusively demonstrates that PsbQ is present in combination with the PsbO, PsbL1, and PsbV proteins in cyanobacterial PSII. Moreover, PsbQ-associated PSII complexes have higher activity and stability relative to those isolated using histidine-tagged CP47, an integral membrane protein. Therefore, we conclude that the presence of PsbQ defines the fully assembled and optimally active form of the enzyme.