The Low Molecular Mass Photosystem II Protein PsbTn Is Important for Light Acclimation
The Low Molecular Mass Photosystem II Protein PsbTn Is Important for Light Acclimation
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DOI：
10.1104/pp.18.01251
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发表时间：
2019-04-01
期刊：
影响因子：
7.4
通讯作者：
Schrodera, Wolfgang P.
中科院分区：
文献类型：
--
作者：
Chen, Yang-Er;Yuan, Shu;Schrodera, Wolfgang P.
光系统II（PSII）是一种超分子复合物，含有30多个蛋白质亚基和大量的辅因子，包括各种色素和醌类以及Mn、Ca、Cl和Fe离子。真核PSII复合物含有许多在细菌中未发现的亚基，包括蛋白质PsbP（PSII）、PsbQ、PsbS和PsbW，以及高度同源的低分子量亚基PsbTn 1和PsbTn 2，其功能目前尚不清楚。为了确定PsbTn1和PsbTn2的功能，我们在拟南芥（Arabidopsis thaliana）中产生了单和双psbTn1和psbTn2敲除突变体。交联和相互免疫共沉淀实验表明，PsbTn是一个位于细胞色素B（559）亚基PsbE旁边的腔内PSII蛋白。PsbTn蛋白的去除降低了氧释放速率和PSII核心磷酸化水平，但增加了PSII对光抑制的敏感性和活性氧的产生。PSII的组装和稳定性不受影响，表明psbTn1 psbTn2双突变体的缺陷是由于结构变化。双突变体表现出更高的非光化学猝灭率的激发态比野生型和单突变体，以及较慢的状态转换动力学和较低的量子产率PSII生长在外地。基于这些结果，我们提出PsbTn蛋白的主要功能是使PSII适应光移或强光。
Photosystem II (PSII) is a supramolecular complex containing over 30 protein subunits and a large set of cofactors, including various pigments and quinones as well as Mn, Ca, Cl, and Fe ions. Eukaryotic PSII complexes contain many subunits not found in their bacterial counterparts, including the proteins PsbP (PSII), PsbQ, PsbS, and PsbW, as well as the highly homologous, low-molecularmass subunits PsbTn1 and PsbTn2 whose function is currently unknown. To determine the function of PsbTn1 and PsbTn2, we generated single and double psbTn1 and psbTn2 knockout mutants in Arabidopsis (Arabidopsis thaliana). Cross linking and reciprocal coimmunoprecipitation experiments revealed that PsbTn is a lumenal PSII protein situated next to the cytochrome b(559 )subunit PsbE. The removal of the PsbTn proteins decreased the oxygen evolution rate and PSII core phosphorylation level but increased the susceptibility of PSII to photoinhibition and the production of reactive oxygen species. The assembly and stability of PSII were unaffected, indicating that the deficiencies of the psbTn1 psbTn2 double mutants are due to structural changes. Double mutants exhibited a higher rate of nonphotochemical quenching of excited states than the wild type and single mutants, as well as slower state transition kinetics and a lower quantum yield of PSII when grown in the field. Based on these results, we propose that the main function of the PsbTn proteins is to enable PSII to acclimate to light shifts or intense illumination.