Molecular Mechanisms of Photoadaptation of Photosystem I Supercomplex from an Evolutionary Cyanobacterial/Algal Intermediate
Molecular Mechanisms of Photoadaptation of Photosystem I Supercomplex from an Evolutionary Cyanobacterial/Algal Intermediate
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DOI：
10.1104/pp.17.01022
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发表时间：
2018-02-01
期刊：
影响因子：
7.4
通讯作者：
Kargula, Joanna M.
中科院分区：
文献类型：
--
作者：
Haniewicz, Patrycja;Abram, Mateusz;Kargula, Joanna M.
来自极端红藻Cyanidioschyzon merolae的单体光系统I-捕光天线复合物I（PSI-LHCI）超复合物代表了蓝细菌PSI反应中心与其绿色藻类/高等植物对应物之间的中间进化联系。结果表明，C. merolae PSI-LHCI超复合物的特征在于在各种极端条件下的稳健性。通过生物化学、光谱、质谱和电子显微镜/单粒子分析的组合，我们剖析了C. merolae PSI-LHCI超复合物：（1）光保护玉米黄质在LHCI天线和PSI反应中心的积累;（2）LHCI天线的结构重塑和有效吸收截面的调整;和（3）两种PSI-LHCI异构体的化学计量的动态重新调整和PSI-LHCI超复合物的低聚状态的变化，伴随着PsaK核心亚基的解离。结果表明，最大的弱光处理C。merolae PSI-LHCI超复合物可以结合多达8个Lhcr天线亚基，其在核心复合物的PsaF/PsaJ侧被组织为两行。在我们的实验条件下，我们发现没有证据的功能耦合的藻胆体与PSI-LHCI超复合物纯化从各种光条件下，这表明推定的关联，该天线与PSI超复合物是不存在的，或可能会失去在纯化过程中。
The monomeric photosystem I-light-harvesting antenna complex I (PSI-LHCI) supercomplex from the extremophilic red alga Cyanidioschyzon merolae represents an intermediate evolutionary link between the cyanobacterial PSI reaction center and its green algal/higher plant counterpart. We show that the C. merolae PSI-LHCI supercomplex is characterized by robustness in various extreme conditions. By a combination of biochemical, spectroscopic, mass spectrometry, and electron microscopy/single particle analyses, we dissected three molecular mechanisms underlying the inherent robustness of the C. merolae PSI-LHCI supercomplex: (1) the accumulation of photoprotective zeaxanthin in the LHCI antenna and the PSI reaction center; (2) structural remodeling of the LHCI antenna and adjustment of the effective absorption cross section; and (3) dynamic readjustment of the stoichiometry of the two PSI-LHCI isomers and changes in the oligomeric state of the PSI-LHCI supercomplex, accompanied by dissociation of the PsaK core subunit. We show that the largest low light-treated C. merolae PSI-LHCI supercomplex can bind up to eight Lhcr antenna subunits, which are organized as two rows on the PsaF/PsaJ side of the core complex. Under our experimental conditions, we found no evidence of functional coupling of the phycobilisomes with the PSI-LHCI supercomplex purified from various light conditions, suggesting that the putative association of this antenna with the PSI supercomplex is absent or may be lost during the purification procedure.