PsbU provides a stable architecture for the oxygen-evolving system in cyanobacterial photosystem II
PsbU provides a stable architecture for the oxygen-evolving system in cyanobacterial photosystem II
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DOI：
10.1021/bi047539k
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发表时间：
2005-09-13
期刊：
影响因子：
2.9
通讯作者：
Pakrasi, HB
中科院分区：
文献类型：
--
作者：
Inoue-Kashino, N;Kashino, Y;Pakrasi, HB
PsbU是蓝细菌和红藻光系统II复合体中的一种腔周蛋白。据认为，PsbU在植物叶绿体中被PsbP或PsbQ功能性取代。在蓝细菌PS II中发现PsbP和PsbQ同源物之后[Thornton等人（2004）Plant Cell 16，2164-2175]，我们使用集胞藻6803的psbU缺失突变体（Delta PsbU）研究了PsbU的功能。与野生型相反，当从生长培养基中消除Ca 2+和Cl-时，Delta PsbU不生长。当仅消除Ca 2+时，Delta PsbU生长良好，而当消除Cl-时，生长速率受到高度抑制。虽然三角洲PsbU生长正常的存在下，这两种离子在中等光，PS II相关的疾病观察如下。(1)突变体细胞对光抑制高度敏感。(2)在低光照下的光利用效率和叶绿素特定的最大放氧速率在德尔塔PsbU细胞比野生型低60%。(3)Δ PsbU细胞中S2态的衰变被减慢。(4)在分离的PS II复合物从三角洲PsbU细胞中，其他三个内腔外源蛋白和电子捐赠率的量急剧下降，表明水氧化系统变得显着不稳定，没有PsbU。此外，在Delta PsbU类囊体膜中的放氧活性在Cl-的情况下被高度抑制，并且60%的活性被NO3-恢复，但不是由SO 42-，表明PsbU具有稳定Cl-以外的功能。在这些结果的基础上，我们得出结论，PsbU是至关重要的水裂解系统的稳定架构，以优化析氧过程的效率。
PsbU is a lumenal peripheral protein in the photosystem II (PS II) complex of cyanobacteria and red algae. It is thought that PsbU is replaced functionally by PsbP or PsbQ in plant chloroplasts. After the discovery of PsbP and PsbQ homologues in cyanobacterial PS II [Thornton et al. (2004) Plant Cell 16, 2164-2175], we investigated the function of PsbU using a psbU deletion mutant (Delta PsbU) of Synechocystis 6803. In contrast to the wild type, Delta PsbU did not grow when both Ca2+ and Cl- were eliminated from the growth medium. When only Ca2+ was eliminated, Delta PsbU grew well, whereas when Cl- was eliminated, the growth rate was highly suppressed. Although Delta PsbU grew normally in the presence of both ions under moderate light, PS II-related disorders were observed as follows. (1) The mutant cells were highly susceptible to photoinhibition. (2) Both the efficiency of light utilization under low irradiance and the chlorophyll-specific maximum rate of oxygen evolution in Delta PsbU cells were 60% lower than those of the wild type. (3) The decay of the S2 state in Delta PsbU cells was decelerated. (4) In isolated PS II complexes from Delta PsbU cells, the amounts of the other three lumenal extrinsic proteins and the electron donation rate were drastically decreased, indicating that the water oxidation system became significantly labile without PsbU. Furthermore, oxygen-evolving activity in Delta PsbU thylakoid membranes was highly suppressed in the absence of Cl-, and 60% of the activity was restored by NO3- but not by SO42-, indicating that PsbU had functions other than stabilizing Cl-. On the basis of these results, we conclude that PsbU is crucial for the stable architecture of the water-splitting system to optimize the efficiency of the oxygen evolution process.