Excitation-energy transfer in heterocysts isolated from the cyanobacterium Anabaena sp. PCC 7120 as studied by time-resolved fluorescence spectroscopy
Excitation-energy transfer in heterocysts isolated from the cyanobacterium Anabaena sp. PCC 7120 as studied by time-resolved fluorescence spectroscopy
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从蓝藻鱼腥藻分离的异形细胞中的激发能量转移。
DOI：
10.1016/j.bbabio.2021.148509
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Akimoto Seiji
中科院分区：
文献类型：
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作者：
Nagao Ryo;Yokono Makio;Ueno Yoshifumi;Nakajima Yoshiki;Suzuki Takehiro;Kato Ka-Ho;Tsuboshita Naoki;Dohmae Naoshi;Shen Jian-Ren;Ehira Shigeki;Akimoto Seiji
异形胞是在氮饥饿条件下形成的丝状异形胞蓝藻，具有非常低的量的光系统II（PSII）复合物比营养细胞。异形胞的分子、形态和生化特征已被研究，然而，异形胞中的激发能动力学仍然是未知的。在这项研究中，我们研究了从蓝藻Anabaenasp中分离的异形胞中色素蛋白复合物的激发-能量-弛豫过程。PCC 7120。在我们的实验条件下，异形胞的类囊体膜没有表现出放氧活性，也没有源于S2 QA-电荷复合的热发光-辉光曲线。二维蓝/SDS-PAGE分析显示四聚体，二聚体，和单体的光系统I（PSI）的复合物，但几乎没有二聚体和单体PSII复合物的异形囊体。在77 K的异囊类囊体的稳态荧光光谱显示的特征PSI荧光和不寻常的PSII荧光不同的PSII二聚体和单体复合物的荧光。在77 K的时间分辨荧光光谱，荧光衰减相关的光谱，表现出不同的PSII和PSI荧光带异形胞和营养类囊体之间。基于这些发现，我们讨论了在异形胞的激发能量转移机制。
Heterocysts are formed in filamentous heterocystous cyanobacteria under nitrogen-starvation conditions, and possess a very low amount of photosystem II (PSII) complexes than vegetative cells. Molecular, morphological, and biochemical characterizations of heterocysts have been investigated; however, excitation-energy dynamics in heterocysts are still unknown. In this study, we examined excitation-energy-relaxation processes of pigment-protein complexes in heterocysts isolated from the cyanobacteriumAnabaenasp. PCC 7120. Thylakoid membranes from the heterocysts showed no oxygen-evolving activity under our experimental conditions and no thermoluminescence-glow curve originating from charge recombination of S2QA−. Two dimensional blue-native/SDS-PAGE analysis exhibits tetrameric, dimeric, and monomeric photosystem I (PSI) complexes but almost no dimeric and monomeric PSII complexes in the heterocyst thylakoids. The steady-state fluorescence spectrum of the heterocyst thylakoids at 77 K displays both characteristic PSI fluorescence and unusual PSII fluorescence different from the fluorescence of PSII dimer and monomer complexes. Time-resolved fluorescence spectra at 77 K, followed by fluorescence decay-associated spectra, showed different PSII and PSI fluorescence bands between heterocysts and vegetative thylakoids. Based on these findings, we discuss excitation-energy-transfer mechanisms in the heterocysts.