Identification of the mobile light-harvesting complex II polypeptides for state transitions in Chlamydomonas reinhardtii
Identification of the mobile light-harvesting complex II polypeptides for state transitions in Chlamydomonas reinhardtii
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DOI：
10.1073/pnas.0509952103
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发表时间：
2006-01-10
影响因子：
11.1
通讯作者：
Minagawa, J
中科院分区：
文献类型：
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作者：
Takahashi, H;Iwai, M;Minagawa, J
光合作用中的状态转换是光系统I（PSI）和光系统II（PSII）之间能量分配的短期平衡机制。当PSII优先激发（状态2），池的移动的捕光复合物II（LHCII）天线蛋白被认为是从PSH迁移到PSI，但生化证据LHCII蛋白和PSI之间的物理关联在状态2是弱的。在这里，使用绿色的奇异果，它具有高容量的状态转换，我们报告的隔离PSI捕光复合物I（LHCI）的超复合物从锁定到状态1和状态2的细胞。我们用温和的去污剂溶解类囊体膜，通过蔗糖密度梯度离心分离蛋白质，并进行梯度洗脱凝胶过滤色谱。三个LHCII多肽与PSI-LHCI超复合物仅在状态2;我们将它们鉴定为两个次要单体LHCII蛋白（CP 26和CP 29）和一个先前未报道的主要LHCII蛋白II型或LhcbM 5。除了主要的三聚体LHCII蛋白之外，这三种LHCII蛋白在转变为状态2时被磷酸化。相应的系统发育树表明，在与PSII相关的LHCII蛋白中，这三个LHCII蛋白与PSI（LHCI）的LHC蛋白最相似。我们的研究结果是重要的，因为CP 26，CP 29，和LhcbM 5，这已被视为只属于PSII复合物，现在假定穿梭PSI和PSII之间的状态转换过程中，从而作为对接位点的三聚体LHCII蛋白在PSI和PSII。
State transition in photosynthesis is a short-term balancing mechanism of energy distribution between photosystem I (PSI) and photosystem II (PSII). When PSII is preferentially excited (state 2), a pool of mobile light-harvesting complex II (LHCII) antenna proteins is thought to migrate from PSH to PSI, but biochemical evidence for a physical association between LHCII proteins and PSI in state 2 is weak. Here, using the green alga Chiamydomonas reinhardtii, which has a high capacity for state transitions, we report the isolation of PSI-light-harvesting complex I (LHCI) supercomplexes from cells locked into state 1 and state 2. We solubilized the thylakoid membranes with a mild detergent, separated the proteins by sucrose density gradient centrifugation, and subjected gradient fractions to gel-filtration chromatography. Three LHCII polypeptides were associated with a PSI-LHCI supercomplex only in state 2; we identified them as two minor monomeric LHCII proteins (CP26 and CP29) and one previously unreported major LHCII protein type II, or LhcbM5. These three LHCII proteins, in addition to the major trimeric LHCII proteins, were phosphorylated upon transition to state 2. The corresponding phylogenetic tree indicates that among the LHCII proteins associated with PSII, these three LHCII proteins are the most similar to the LHC proteins for PSI (LHCI). Our results are important because CP26, CP29, and LhcbM5, which have been viewed as belonging solely to the PSII complex, are now postulated to shuttle between PSI and PSII during state transitions, thereby acting as docking sites for the trimeric LHCII proteins in both PSI and PSII.