Arabidopsis Tic62 and Ferredoxin-NADP(H) Oxidoreductase Form Light-Regulated Complexes That Are Integrated into the Chloroplast Redox Poise
Arabidopsis Tic62 and Ferredoxin-NADP(H) Oxidoreductase Form Light-Regulated Complexes That Are Integrated into the Chloroplast Redox Poise
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DOI：
10.1105/tpc.109.069815
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发表时间：
2009-12-01
期刊：
影响因子：
11.6
通讯作者：
Boelter, B.
中科院分区：
文献类型：
--
作者：
Benz, J. P.;Stengel, A.;Boelter, B.
Tictranslocon催化核编码的前蛋白穿过叶绿体内被膜的转运，Tictranslocon由Tic 110、Tic 40、Tic 62、Tic 55、Tic 32、Tic 20和Tic 22组成。Tic 62是一种氧化还原传感器，它依赖于氧化还原在被膜和基质之间穿梭，并与光合作用蛋白铁氧还蛋白-NADP（H）氧化还原酶（FNR）特异性相互作用。然而，这种密切关系的性质至今仍是个谜。Tic 62在类囊体中的一个假定的额外定位要求进一步研究该功能如何参与各自的氧化还原传感途径以及与其伴侣蛋白的相互作用。因此，无论是与FNR的协会和第三，类囊体结合池的Tic 62的生理作用进行了详细的研究。共表达分析表明，Tic 62与参与光合功能和蛋白质周转的基因具有相似的表达模式。在类囊体，Tic 62和FNR形成高分子量的复合物，不参与光合电子传递，但动态调节的光信号和基质pH值。结构分析表明，Tic 62结合FNR的黄素蛋白的一种新的结合模式，从疏水相互作用的主要贡献。此外，在不存在Tic 62的情况下，FNR的膜结合和稳定性急剧降低。我们的结论是，Tic 62代表一个主要的FNR相互作用的合作伙伴，不仅在信封和基质中，而且在类囊体的拟南芥，也许所有的开花植物。与Tic 62的结合使FNR稳定，并参与其动态和光依赖性膜束缚。
Translocation of nuclear-encoded preproteins across the inner envelope of chloroplasts is catalyzed by the Tictranslocon, consisting of Tic110, Tic40, Tic62, Tic55, Tic32, Tic20, and Tic22. Tic62 was proposed to act as a redox sensor of the complex because of its redox-dependent shuttling between envelope and stroma and its specific interaction with the photosynthetic protein ferredoxin-NADP(H) oxidoreductase (FNR). However, the nature of this close relationship so far remained enigmatic. A putative additional localization of Tic62 at the thylakoids mandated further studies examining how this feature might be involved in the respective redox sensing pathway and the interaction with its partner protein. Therefore, both the association with FNR and the physiological role of the third, thylakoid-bound pool of Tic62 were investigated in detail. Coexpression analysis indicates that Tic62 has similar expression patterns as genes involved in photosynthetic functions and protein turnover. At the thylakoids, Tic62 and FNR form high molecular weight complexes that are not involved in photosynthetic electron transfer but are dynamically regulated by light signals and the stromal pH. Structural analyses reveal that Tic62 binds to FNR in a novel binding mode for flavoproteins, with a major contribution from hydrophobic interactions. Moreover, in absence of Tic62, membrane binding and stability of FNR are drastically reduced. We conclude that Tic62 represents a major FNR interaction partner not only at the envelope and in the stroma, but also at the thylakoids of Arabidopsis thaliana and perhaps all flowering plants. Association with Tic62 stabilizes FNR and is involved in its dynamic and light-dependent membrane tethering.