Evidence of the supercomplex organization of photosystem II and light-harvesting complexes in Nannochloropsis granulata.
Evidence of the supercomplex organization of photosystem II and light-harvesting complexes in Nannochloropsis granulata.
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微拟球藻中光系统 II 和光捕获复合体的超复合体组织的证据。
DOI：
10.1007/s11120-017-0438-z
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Tanaka A.
中科院分区：
文献类型：
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作者：
Umetani I;Kunugi M;Yokono M;Takabayashi A;Tanaka A.
在光合微藻中发现了多种捕光复合体，它们起源于原生红藻的次生内共生。然而，LHC和光系统I（PSI）和光系统II（PSII）在这些微藻之间的关联还没有完全了解。真鞭毛藻门是红藻的一个分支，其光合作用机制似乎具有独特的组织结构，仅由叶绿素和类胡萝卜素组成，与其他密切相关的类群相比是非典型的。本研究采用透明非变性（CN）PAGE结合二维（2D）SDS-PAGE技术，研究了微拟球藻（Nannochloropsis granulata）色素蛋白复合物的超分子结构。我们的研究结果表明，两个缓慢迁移的绿色带，对应于PSII超复合物，其中包括反应中心和LHC。这些绿色谱带也被表征为PSII复合物通过它们的低温荧光发射光谱。通过2D CN/SDS-PAGE解析的PSII-LHC的蛋白亚基通过质谱分析，并鉴定出四种不同的LHC蛋白。对鉴定的LHC蛋白序列的系统发育分析显示，它们属于四个不同的Lhc组：（1）胁迫相关的Lhcx蛋白，（2）叶绿素岩藻黄素/c结合的Lhcf蛋白，（3）红移的Chromeralight-harvesting蛋白（Red-CLH），和（4）Lhcr蛋白，其通常在具有红色藻质体的生物体中发现。这是第一个报告显示的证据，色素蛋白超复合物组成的PSII和LHC，并确定PSII相关的LHC蛋白inNannochloropsis。
Diverse light-harvesting complexes (LHCs) have been found in photosynthetic microalgae that originated from secondary endosymbiosis involving primary red algae. However, the associations between LHCs and photosystem I (PSI) and photosystem II (PSII) in these microalgae are not fully understood. Eustigmatophyta is a red algal lineage that appears to have a unique organization in its photosynthetic machinery, consisting of only chlorophyllaand carotenoids that are atypical compared with other closely related groups. In this study, the supramolecular organization of pigment–protein complexes in the eustigmatophyte alga,Nannochloropsis granulatawas investigated using Clear Native (CN) PAGE coupled with two-dimensional (2D) SDS-PAGE. Our results showed two slowly migrating green bands that corresponded to PSII supercomplexes, which consisted of reaction centers and LHCs. These green bands were also characterized as PSII complexes by their low temperature fluorescence emission spectra. The protein subunits of the PSII–LHC resolved by 2D CN/SDS-PAGE were analyzed by mass spectrometry, and four different LHC proteins were identified. Phylogenetic analysis of the identified LHC protein sequences revealed that they belonged to four different Lhc groups; (1) stress-related Lhcx proteins, (2) fucoxanthin chlorophylla/c-binding Lhcf proteins, (3) red-shiftedChromeralight-harvesting proteins (Red-CLH), and (4) Lhcr proteins, which are commonly found in organisms possessing red algal plastids. This is the first report showing evidence of a pigment–protein supercomplex consisting of PSII and LHCs, and to identify PSII-associated LHC proteins inNannochloropsis.