The Core of Chloroplast Nucleoids Contains Architectural SWIB Domain Proteins[W][OA]
The Core of Chloroplast Nucleoids Contains Architectural SWIB Domain Proteins[W][OA]
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DOI：
10.1105/tpc.112.099721
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发表时间：
2012-07
期刊：
影响因子：
11.6
通讯作者：
J. Melonek;A. Matros;Mirl Trösch;H. Mock;K. Krupinska
中科院分区：
文献类型：
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作者：
J. Melonek;A. Matros;Mirl Trösch;H. Mock;K. Krupinska
利用双向凝胶电泳和质谱技术对菠菜叶绿体中具有转录活性的染色体进行了分析，以确定与类核核心结构有关的蛋白质。SWI/SNF复合体B结构域蛋白可能与细菌核相关蛋白具有相同的功能，参与了类核结构的形成。利用双向凝胶电泳和质谱技术对菠菜叶绿体中转录活性较高的染色体片段进行了分析，以确定与类核核心结构有关的蛋白质。在这些质体核相关候选蛋白中，鉴定出一个12-kD SWI/SNF复合物B结构域蛋白。它属于一个低分子质量SWIB结构域蛋白亚群，在拟南芥中有6个成员（SWIB-1至SWIB-6），预测定位在两个含dna的细胞器中。其中四种绿色/红色荧光蛋白融合物被证明是针对叶绿体的，它们在叶绿体中彼此共定位，并与质体包膜DNA结合蛋白在质体类核对应的结构中共定位。对于SWIB-6和SWIB-4，可以分别在线粒体和细胞核中观察到二次定位。SWIB-4在SWIB结构域附近有一个组蛋白H1基序，并被证明与DNA结合。此外，重组SWIB-4蛋白被证明可以诱导类核的压实和凝聚，并在功能上补充缺乏组蛋白样类核结构蛋白H-NS的大肠杆菌突变体。
The transcriptionally active chromosome from spinach chloroplasts was analyzed by two-dimensional gel electrophoresis and mass spectrometry to identify proteins involved in structuring of the nucleoid core. SWI/SNF complex B domain–containing proteins were identified that might be functional equivalents of the bacterial nucleoid-associated proteins involved in shaping of nucleoid architecture. A highly enriched fraction of the transcriptionally active chromosome from chloroplasts of spinach (Spinacia oleracea) was analyzed by two-dimensional gel electrophoresis and mass spectrometry to identify proteins involved in structuring of the nucleoid core. Among such plastid nucleoid-associated candidate proteins a 12-kD SWIB (SWI/SNF complex B) domain–containing protein was identified. It belongs to a subgroup of low molecular mass SWIB domain proteins, which in Arabidopsis thaliana has six members (SWIB-1 to SWIB-6) with predictions for localization in the two DNA-containing organelles. Green/red fluorescent protein fusions of four of them were shown to be targeted to chloroplasts, where they colocalize with each other as well as with the plastid envelope DNA binding protein in structures corresponding to plastid nucleoids. For SWIB-6 and SWIB-4, a second localization in mitochondria and nucleus, respectively, could be observed. SWIB-4 has a histone H1 motif next to the SWIB domain and was shown to bind to DNA. Moreover, the recombinant SWIB-4 protein was shown to induce compaction and condensation of nucleoids and to functionally complement a mutant of Escherichia coli lacking the histone-like nucleoid structuring protein H-NS.