A thylakoid membrane-bound and redox-active rubredoxin (RBD1) functions in de novo assembly and repair of photosystem II
A thylakoid membrane-bound and redox-active rubredoxin (RBD1) functions in de novo assembly and repair of photosystem II
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DOI：
10.1073/pnas.1903314116
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发表时间：
2019-08-13
影响因子：
11.1
通讯作者：
Niyogi, Krishna K.
中科院分区：
文献类型：
--
作者：
Garcia-Cerdan, Jose G.;Furst, Ariel L.;Niyogi, Krishna K.
光系统II（PSII）经历频繁的光氧化损伤，如果不修复，损害光合活性和生长。光合生物如何在从头组装和修复过程中保护脆弱的PSII中间复合物仍然知之甚少。在这里，我们报告的遗传和生化特性的叶绿体定位rubredoxin 1（RBD 1），PSII装配因子含有氧化还原活性rubredoxin结构域和一个单一的C-末端跨膜α-螺旋（TMH）结构域。RBD 1是一种完整的类囊体膜蛋白，在基质层组分中富集，红氧蛋白结构域暴露在基质侧。RBD 1还与含有细胞色素B的PSII中间复合物相互作用（559）。补充衣原体reinhardtii（以下简称衣原体）RBD 1缺陷型2pac突变体与编码RBD 1蛋白截短和定点突变的构建体表明，TMH结构域是必不可少的从头PSII组装，而rubredoxin结构域参与PSII修复。红氧还蛋白结构域表现出+114 mV的氧化还原中点电位，并且在体外擅长1-电子转移到替代细胞色素c。氧化RBD 1的还原是NADPH依赖性的，并且可以在体外由铁氧还蛋白-NADP+还原酶（FNR）介导。我们认为RBD 1与细胞色素B（559）一起参与保护PSII中间复合物在从头组装和修复过程中免受光氧化损伤。RBD 1的这种作用与其在光合生物中的进化保守性以及它在光合真核生物中是必不可少的这一事实是一致的。
Photosystem II (PSII) undergoes frequent photooxidative damage that, if not repaired, impairs photosynthetic activity and growth. How photosynthetic organisms protect vulnerable PSII intermediate complexes during de novo assembly and repair remains poorly understood. Here, we report the genetic and biochemical characterization of chloroplast-located rubredoxin 1 (RBD1), a PSII assembly factor containing a redox-active rubredoxin domain and a single C-terminal transmembrane alpha-helix (TMH) domain. RBD1 is an integral thylakoid membrane protein that is enriched in stroma lamellae fractions with the rubredoxin domain exposed on the stromal side. RBD1 also interacts with PSII intermediate complexes containing cytochrome b(559). Complementation of the Chlamydomonas reinhardtii (hereafter Chlamydomonas) RBD1-deficient 2pac mutant with constructs encoding RBD1 protein truncations and site-directed mutations demonstrated that the TMH domain is essential for de novo PSII assembly, whereas the rubredoxin domain is involved in PSII repair. The rubredoxin domain exhibits a redox midpoint potential of +114 mV and is proficient in 1-electron transfers to a surrogate cytochrome c in vitro. Reduction of oxidized RBD1 is NADPH dependent and can be mediated by ferredoxin-NADP+ reductase (FNR) in vitro. We propose that RBD1 participates, together with the cytochrome b(559), in the protection of PSII intermediate complexes from photooxidative damage during de novo assembly and repair. This role of RBD1 is consistent with its evolutionary conservation among photosynthetic organisms and the fact that it is essential in photosynthetic eukaryotes.