PsbN Is Required for Assembly of the Photosystem II Reaction Center in Nicotiana tabacum[W]
PsbN Is Required for Assembly of the Photosystem II Reaction Center in Nicotiana tabacum[W]
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DOI：
10.1105/tpc.113.120444
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发表时间：
2014-03
期刊：
影响因子：
11.6
通讯作者：
Salar Torabi;Pavan Umate;Nikolay Manavski;Magdalena Plöchinger;Laura Kleinknecht;Hanumakumar Bogireddi
中科院分区：
文献类型：
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作者：
Salar Torabi;Pavan Umate;Nikolay Manavski;Magdalena Plöchinger;Laura Kleinknecht;Hanumakumar Bogireddi
叶绿体编码的低分子量膜蛋白PsbN的高度保守的C末端暴露在非贴伏的类囊体片基质中，表明它不是光系统II(PSII)的一部分。大量的PSbN突变分析表明，∆是异源二聚体反应中心的组装和光抑制后的修复过程所必需的。叶绿体编码的低分子量蛋白质PsbN被注释为光系统II(PSII)亚单位。为了阐明PsbN的定位和功能，我们提出了抗体，并在PsbN中双向插入了抗性盒。烟草同源体突变体∆PsbN-F和∆PsbN-R表现出基本相同的PSII缺陷。突变体对光非常敏感，无法从光抑制中恢复。虽然两个突变体的PSⅡ蛋白合成没有明显变化，但与野生型相比，两个突变体仅积累了25%的∼蛋白。PSII前复合体以正常速率组装，但突变体中不能有效地形成异二聚体反应中心(RCS)和高阶PSII组装。PsbN基因与核基因组中叶绿体转运肽序列的融合表达补充了∆的突变体。PsbN是一种定位于基质板层的跨膜结合多肽，其高度保守的C末端暴露在基质中。大量的PsbN已经存在于暗生长的幼苗中。我们的数据证明PsbN不是PSII的组成亚基，但对于光抑制修复和PSII RC的有效组装是必需的。
The highly conserved C terminus of the plastid-encoded low molecular weight membrane protein PsbN is exposed to the stroma of nonappressed thylakoid lamellae, indicating that it is not part of photosystem II (PSII). Extensive ∆psbN mutant analyses provide evidence that PsbN is specifically required for assembly of the heterodimeric PSII reaction center and the repair process after photoinhibition. The chloroplast-encoded low molecular weight protein PsbN is annotated as a photosystem II (PSII) subunit. To elucidate the localization and function of PsbN, encoded on the opposite strand to the psbB gene cluster, we raised antibodies and inserted a resistance cassette into PsbN in both directions. Both homoplastomic tobacco (Nicotiana tabacum) mutants ∆psbN-F and ∆psbN-R show essentially the same PSII deficiencies. The mutants are extremely light sensitive and failed to recover from photoinhibition. Although synthesis of PSII proteins was not altered significantly, both mutants accumulated only ∼25% of PSII proteins compared with the wild type. Assembly of PSII precomplexes occurred at normal rates, but heterodimeric PSII reaction centers (RCs) and higher order PSII assemblies were not formed efficiently in the mutants. The ∆psbN-R mutant was complemented by allotopic expression of the PsbN gene fused to the sequence of a chloroplast transit peptide in the nuclear genome. PsbN represents a bitopic trans-membrane peptide localized in stroma lamellae with its highly conserved C terminus exposed to the stroma. Significant amounts of PsbN were already present in dark-grown seedling. Our data prove that PsbN is not a constituent subunit of PSII but is required for repair from photoinhibition and efficient assembly of the PSII RC.