Chloroplast-encoded polypeptide PsbT is involved in the repair of primary electron acceptor QA of photosystem II during photoinhibition in Chlamydomonas reinhardtii
Chloroplast-encoded polypeptide PsbT is involved in the repair of primary electron acceptor QA of photosystem II during photoinhibition in Chlamydomonas reinhardtii
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DOI：
10.1074/jbc.m606763200
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发表时间：
2007-03-09
影响因子：
4.8
通讯作者：
Takahashi, Yuichiro
中科院分区：
文献类型：
--
作者：
Ohnishi, Norikazu;Kashino, Yasuhiro;Takahashi, Yuichiro
PsbT是一种小的叶绿体编码的疏水性多肽，与光系统II（PSII）反应中心的D1/D2异源二聚体相关，是光损伤的PSII的有效翻译后修复所必需的。在这里，我们详细讨论了在莱茵衣藻野生型和三角洲psbT细胞中的作用，通过分析PSII的活动，PSII蛋白的组装，和PSII的氧化还原组分在光抑制和修复。强光照射15 min使PSII的电子传递活性和Q_1光还原活性降低50%，使锰原子量减少20%，但对PSII蛋白质的稳态水平、脱镁叶绿素（Pheo（D_1））的光还原和质体醌（Q_1）的结合量没有影响。表明PSII活性的降低主要是由于抑制了pheo（D1）向Q（A）的电子传递。在野生型细胞中，我们观察到通过PSII和Q，光还原的电子转移活性的平行恢复，这表明Q，活动的恢复是PSII修复的限速步骤之一。在Delta psbT细胞中，通过PSII的电子转移活性和QA光还原活性的修复都受到损害，但PSII蛋白质周转不受影响。此外，在纯化过程中，约一半的QA从PSI 1核心复合物中损失。由于PsbT与D2上的QA结合区密切相关，我们建议这种多肽通过稳定QA结合区的结构来增强QA光还原的有效恢复。
PsbT is a small chloroplast-encoded hydrophobic polypeptide associated with the D1/D2 heterodimer of the photosystem II (PSII) reaction center and is required for the efficient posttranslational repair of photodamaged PSII. Here we addressed that role in detail in Chlamydomonas reinhardtii wild type and Delta psbT cells by analyzing the activities of PSII, the assembly of PSII proteins, and the redox components of PSII during photoinhibition and repair. Strong illumination of cells for 15 min decreased the activities of electron transfer through PSII and Q, photoreduction by 50%, and it reduced the amount of atomic manganese by 20%, but it did not affect the steadystate level of PSII proteins, photoreduction of pheophytin (pheo(D1)), and the amount of bound plastoquinone (Q,), indicating that the decrease in PSII activity resulted mainly from inhibition of the electron transfer from pheo(D1) to Q(A). In wild type cells, we observed parallel recovery of electron transfer activity through PSII and Q, photoreduction, suggesting that the recovery of Q, activity is one of the rate-limiting steps of PSII repair. In Delta psbT cells, the repairs of electron transfer activity through PSII and of QA photoreduction activity were both impaired, but PSII protein turnover was unaffected. Moreover, about half the QA was lost from the PSI1 core complex during purification. Since PsbT is intimately associated with the QA-binding region on D2, we propose that this polypeptide enhances the efficient recovery of QA photoreduction by stabilizing the structure of the Q.A-binding region.