Light- and pH-dependent structural changes in the PsbS subunit of photosystem II
Light- and pH-dependent structural changes in the PsbS subunit of photosystem II
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DOI：
10.1073/pnas.2533072100
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发表时间：
2003-12-09
影响因子：
11.1
通讯作者：
Szabò, I
中科院分区：
文献类型：
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作者：
Bergantino, E;Segalla, A;Szabò, I
在高等植物中，光系统II（PSII）的PsbS亚基在pH和叶黄素依赖的非光化学猝灭过量吸收的光能中起着至关重要的作用，从而有助于对抗光抑制的防御机制。我们确定了玉米PsbS的氨基酸序列，并产生了一种抗体，该抗体以高特异性识别位于第二和第三假定螺旋之间的基质暴露环中的蛋白质区域。通过这种抗血清，各种高等植物的类囊体膜揭示了一个42 kDa的蛋白带的存在下，表明21 kDa的PsbS蛋白的二聚体的形成。与其他抗血清的交联实验和免疫印迹似乎排除了与其他PSII蛋白组分形成异二聚体的可能性。在孤立的类囊体膜的PsbS单体/二聚体的比例被发现以可逆的方式与管腔pH值的变化，在酸性和碱性pH值的二聚体的单体是普遍的形式。在完整的叶绿体和整个植物，二聚体到单体的转化是可逆的光诱导，已知引起管腔酸化。蔗糖梯度离心揭示了普遍的关联PsbS单体和二聚体与捕光复合物和PSII核心复合物，分别。光诱导的PsbS亚基的四级结构的变化的存在的发现可能有助于了解PsbS行动的机制，在非光化学猝灭。
In higher plants, the PsbS subunit of photosystem II (PSII) plays a crucial role in pH- and xanthophyll-dependent nonphotochemical quenching of excess absorbed light energy, thus contributing to the defense mechanism against photoinhibition. We determined the amino acid sequence of Zea mays PsbS and produced an antibody that recognizes with high specificity a region of the protein located in the stroma-exposed loop between the second and third putative helices. By means of this antiserum, the thylakoid membranes of various higher plant species revealed the presence of a 42-kDa protein band, indicating the formation of a dimer of the 21-kDa PsbS protein. Crosslinking experiments and immunoblotting with other antisera seem to exclude the formation of a heterodimer with other PSII protein components. The PsbS monomer/dimer ratio in isolated thylakoid membranes was found to vary with luminal pH in a reversible manner, the monomer being the prevalent form at acidic and the dimer at alkaline pH. In intact chloroplasts and whole plants, dimer-to-monomer conversion is reversibly induced by light, known to cause luminal acidification. Sucrose-gradient centrifugation revealed a prevalent association of the PsbS monomer and dimer with light-harvesting complex and PSII core complexes, respectively. The finding of the existence of a light-induced change in the quaternary structure of the PsbS subunit may contribute to understanding the mechanism of PsbS action during nonphotochemical quenching.