Phycobilisomes Harbor FNRL in Cyanobacteria
Phycobilisomes Harbor FNRL in Cyanobacteria
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DOI：
10.1128/mbio.00669-19
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发表时间：
2019-03-01
期刊：
影响因子：
6.4
通讯作者：
Blankenship, Robert E.
中科院分区：
文献类型：
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作者：
Liu, Haijun;Weisz, Daniel A.;Blankenship, Robert E.
蓝藻藻胆体（PBS）是光合作用的天线复合体，收集光能并将其提供给两个反应中心（RC），在那里开始光化学。PBS可根据别藻蓝蛋白（APC）的存在分为两种类型：CpcG-PBS和Cod-PBS。由于CpcL-PBS的准确蛋白质组成仍然不清楚，我们在这里描述了它的分离和表征蓝藻集胞藻属6803菌株。我们发现，铁氧还蛋白-NADP氧化还原酶（或FNRL），参与循环电子传递和电子传递链的终端步骤在产氧光合作用，是紧密相关的CpcL-PBS以及与CpcG-PBS。室温和低温荧光分析表明，在没有APC的情况下，CpcL-PBS作为终端能量发射体在669 nm处发生红移发射。SDS-PAGE和定量质谱法显示，与CpcG-PBS棒相比，CpcL-PBS中FNRL和CpcC 2（一种棒连接蛋白）的含量增加，表明CpcL-PBS棒长度延长，并且其与CpcG-PBS的潜在功能差异。此外，我们将同位素编码的交联质谱与计算蛋白质结构预测和结构建模相结合，以产生FNRL-PBS结合模型，该模型由FNRL的K-69和CpcB的N末端之间的两个交联（PBS中的一个组分，CpcG-PBS和CpcL-PBS中的一个组分（交联1））以及FNRL和CpcB的N末端之间的两个交联（交联2））支持。我们的数据提供了一种新的功能组装形式的藻胆蛋白和FNRL与藻蓝蛋白在CpcG-PBS和CpcL-PBS.IMPORTANCE的密切关联的分子水平的描述蓝藻捕光复合物PBS是必不可少的光化学反应和平衡能量流的ATP和NADPH形式的碳固定。我们分离了一种没有别藻蓝蛋白核心的新型PBS（即，CpcL-PBS）。CpcL-PBS含有光谱红移的发色团，使有效的能量转移到叶绿素分子的反应中心，并增加FNRL含量与各种杆长度。FNRL与CpcG-PBS和CpcL-PBS两者的密切关联的鉴定为其通过非循环和循环电子传递微调光能转移和碳固定的调节作用带来了新的见解。
Cyanobacterial phycobilisomes (PBSs) are photosynthetic antenna complexes that harvest light energy and supply it to two reaction centers (RCs) where photochemistry starts. PBSs can be classified into two types, depending on the presence of allophycocyanin (APC): CpcG-PBS and Cod-PBS. Because the accurate protein composition of CpcL-PBS remains unclear, we describe here its isolation and characterization from the cyanobacterium Synechocystis sp. strain 6803. We found that ferredoxin-NADP oxidoreductase (or FNRL), an enzyme involved in both cyclic electron transport and the terminal step of the electron transport chain in oxygenic photosynthesis, is tightly associated with CpcL-PBS as well as with CpcG-PBS. Room temperature and low-temperature fluorescence analyses show a red-shifted emission at 669 nm in CpcL-PBS as a terminal energy emitter without APC. SDS-PAGE and quantitative mass spectrometry reveal an increased content of FNRL and CpcC2, a rod linker protein, in CpcL-PBS compared to that of CpcG-PBS rods, indicative of an elongated CpcL-PBS rod length and its potential functional differences from CpcG-PBS. Furthermore, we combined isotope-encoded cross-linking mass spectrometry with computational protein structure predictions and structural modeling to produce an FNRL-PBS binding model that is supported by two cross-links between K-69 of FNR L and the N terminus of CpcB, one component in PBS, in both CpcG-PBS and CpcL-PBS (cross-link 1), and between the N termini of FNRL and CpcB (cross-link 2). Our data provide a novel functional assembly form of phycobiliproteins and a molecular-level description of the close association of FNRL with phycocyanin in both CpcG-PBS and CpcL-PBS.IMPORTANCE Cyanobacterial light-harvesting complex PBSs are essential for photochemistry in light reactions and for balancing energy flow to carbon fixation in the form of ATP and NADPH. We isolated a new type of PBS without an allophycocyanin core (i.e., CpcL-PBS). CpcL-PBS contains both a spectral red-shifted chromophore, enabling efficient energy transfer to chlorophyll molecules in the reaction centers, and an increased FNRL content with various rod lengths. Identification of a close association of FNRL with both CpcG-PBS and CpcL-PBS brings new insight to its regulatory role for fine-tuning light energy transfer and carbon fixation through both noncyclic and cyclic electron transport.