Bimodal intramolecular excitation energy transfer in a multichromophore photosynthetic model system: hybrid fusion proteins comprising natural phycobilin- and artificial chlorophyll-binding domains.
Bimodal intramolecular excitation energy transfer in a multichromophore photosynthetic model system: hybrid fusion proteins comprising natural phycobilin- and artificial chlorophyll-binding domains.
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DOI：
10.1021/ja405617c
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发表时间：
2013-08
影响因子：
15
通讯作者：
Xiao-Li Zeng;Kun Tang;N. Zhou;Ming Zhou;H. Hou;H. Scheer;K. Zhao;D. Noy
中科院分区：
文献类型：
--
作者：
Xiao-Li Zeng;Kun Tang;N. Zhou;Ming Zhou;H. Hou;H. Scheer;K. Zhao;D. Noy
蓝藻和红藻的藻胆体是一种高效的外围捕光复合体，它们通过一系列激发能量传递步骤捕获光能，并通过多个藻胆素生色团传递到核心光系统的叶绿素。在这项工作中，我们通过构建天然藻胆体-光系统复合体的简单功能类似物来关注这一过程的最后一步，这些复合体基于含有藻胆素和叶绿素或卟啉结合域的双色蛋白复合体。前者基于藻胆体L(CM)核膜连接子的N-末端生色团结合域APCE(1-240)，后者基于从头设计的四螺旋束蛋白HP7，最初计划作为一种类似b型细胞色素的高亲和力血红素结合蛋白。我们将一个修饰的HP7蛋白序列与APCEΔ融合，APCE是APCE(1-240)的一个水溶性片段，通过切割一个假定的疏水环序列77-153.HP7被融合到APCEΔ的N-端或C-端，或插入在残基76-78之间，从而取代了天然的疏水环区。我们描述了两个独特的系统的组装、光谱特征和分子内激发能量转移：在第一个系统中，短波长吸收锌中卟啉结合到HP7结构域，并为结合到APCE结构域的长波吸收藻蓝胆素提供激发能量；在第二个系统中，短波吸收藻红蛋白结合到APCE结构域，作为长波长吸收锌细菌叶绿素结合到HP7结构域的激发能量供体。所有构建和测试的体系都表现出显着的分子内荧光共振能量转移，产率从21%到50%不等。这证实了我们研究环链和开链四吡咯之间的EET的模块化、共价方法是合理的，并可能扩展到更大的模拟蓝藻捕光的结构。设计、构建和表征过程展示了在构建这样的模型系统方面的许多进展，特别是在我们控制蛋白质系统的折叠和聚集状态的能力方面。同时，它强调了利用基于蛋白质的系统的多功能性和灵活性，将多种颜料组装成有效的捕光阵列，并调节多发色团系统的光谱性质的潜力。
The phycobilisomes of cyanobacteria and red-algae are highly efficient peripheral light-harvesting complexes that capture and transfer light energy in a cascade of excitation energy transfer steps through multiple phycobilin chromophores to the chlorophylls of core photosystems. In this work, we focus on the last step of this process by constructing simple functional analogs of natural phycobilisome-photosystem complexes that are based on bichromophoric protein complexes comprising a phycobilin- and a chlorophyll- or porphyrin-binding domain. The former is based on ApcE(1-240), the N-terminal chromophore-binding domain of the phycobilisome's L(CM) core-membrane linker, and the latter on HP7, a de novo designed four-helix bundle protein that was originally planned as a high-affinity heme-binding protein, analogous to b-type cytochromes. We fused a modified HP7 protein sequence to ApcEΔ, a water-soluble fragment of ApcE(1-240) obtained by excising a putative hydrophobic loop sequence of residues 77-153. HP7 was fused either to the N- or the C-terminus of ApcEΔ or inserted between residues 76 and 78, thereby replacing the native hydrophobic loop domain. We describe the assembly, spectral characteristics, and intramolecular excitation energy transfer of two unique systems: in the first, the short-wavelength absorbing zinc-mesoporphyrin is bound to the HP7 domain and serves as an excitation-energy donor to the long-wavelength absorbing phycocyanobilin bound to the ApcE domain; in the second, the short-wavelength absorbing phycoerythrobilin is bound to the ApcE domain and serves as an excitation energy donor to the long-wavelength absorbing zinc-bacteriochlorophyllide bound to the HP7 domain. All the systems that were constructed and tested exhibited significant intramolecular fluorescence resonance energy transfer with yields ranging from 21% to 50%. This confirms that our modular, covalent approach for studying EET between the cyclic and open chain tetrapyrroles is reasonable, and may be extended to larger structures mimicking light-harvesting in cyanobacteria. The design, construction, and characterization process demonstrated many of the advances in constructing such model systems, particularly in our ability to control the fold and aggregation state of protein-based systems. At the same time, it underlines the potential of exploiting the versatility and flexibility of protein-based systems in assembling multiple pigments into effective light-harvesting arrays and tuning the spectral properties of multichromophore systems.