Absence of the PsbQ protein results in destabilization of the PsbV protein and decreased oxygen evolution activity in cyanobacterial photosystem II
Absence of the PsbQ protein results in destabilization of the PsbV protein and decreased oxygen evolution activity in cyanobacterial photosystem II
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DOI：
10.1074/jbc.m603188200
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发表时间：
2006-07-28
影响因子：
4.8
通讯作者：
Pakrasi, Himadri B.
中科院分区：
文献类型：
--
作者：
Kashino, Yasuhiro;Inoue-Kashino, Natsuko;Pakrasi, Himadri B.
我们先前已经报道了蓝藻光系统II（PS II）含有与PsbQ同源的蛋白质，PsbQ是在高等植物和绿色藻类PS II中发现的外源性17-kDa蛋白质（Kashino，Y.，Lauber，W. M.，卡罗尔，J.A.，王建奎，Whitmarsh，J.，Satoh，K.，美国，和Pakrasi，H. B。（2002）Biochemistry 41，8004 - 8012），并且其对水氧化机制具有调节作用（Thornton，L. E、Ohkawa，H.，鲁塞，J.L.，卡希诺，Y.，Keren，N.，和Pakrasi，H. B。（2004）Plant Cell 16，2164 - 2175）。在这项工作中，PsbQ的定位和功能进行了评估，使用蓝藻集胞藻属PCC 6803。从预测的序列，蓝藻PsbQ预计是一个脂蛋白的类囊体膜的腔侧。事实上，在这项工作中的实验表明，在Triton X-114分级的类囊体膜，PsbQ在疏水相分配，和胰蛋白酶消化显示，PsbQ是高度暴露于类囊体膜的腔空间。对psbQ缺失突变体（Delta psbQ）进行详细的功能测定以分析其水氧化机制。从Delta psbQ突变体细胞中纯化的PS II复合物具有受损的析氧活性，并且对NH（2）OH非常敏感，这表明水氧化机制的不稳定性。此外，细胞色素c（550）（PsbV）蛋白部分解离纯化的Delta psbQ PS II复合物，这表明PsbQ有助于PsbV在蓝藻PS II的稳定性。因此，我们得出结论，PsbQ的主要功能是稳定PsbV蛋白，从而有助于保护水氧化机制的催化Mn-4-Ca-1-Cl-x簇。
We have previously reported that cyanobacterial photosystem II ( PS II) contains a protein homologous to PsbQ, the extrinsic 17-kDa protein found in higher plant and green algal PS II ( Kashino, Y., Lauber, W. M., Carroll, J.A., Wang, Q., Whitmarsh, J., Satoh, K., and Pakrasi, H. B. ( 2002) Biochemistry 41, 8004 - 8012) and that it has regulatory role( s) on the water oxidation machinery ( Thornton, L. E., Ohkawa, H., Roose, J. L., Kashino, Y., Keren, N., and Pakrasi, H. B. ( 2004) Plant Cell 16, 2164 - 2175). In this work, the localization and the function of PsbQ were assessed using the cyanobacterium Synechocystis sp. PCC 6803. From the predicted sequence, cyanobacterial PsbQ is expected to be a lipoprotein on the luminal side of the thylakoid membrane. Indeed, experiments in this work show that upon Triton X-114 fractionation of thylakoid membranes, PsbQ partitioned in the hydrophobic phase, and trypsin digestion revealed that PsbQ was highly exposed to the luminal space of thylakoid membranes. Detailed functional assays were conducted on the psbQ deletion mutant ( Delta psbQ) to analyze its water oxidation machinery. PS II complexes purified from Delta psbQ mutant cells had impaired oxygen evolution activity and were remarkably sensitive toNH(2)OH, which indicates destabilization of the water oxidation machinery. Additionally, the cytochrome c(550) ( PsbV) protein partially dissociated from purified Delta psbQ PS II complexes, suggesting that PsbQ contributes to the stability of PsbV in cyanobacterial PS II. Therefore, we conclude that the major function of PsbQ is to stabilize the PsbV protein, thereby contributing to the protection of the catalytic Mn-4-Ca-1-Cl-x cluster of the water oxidation machinery.