Spectroscopic properties of PSI-IsiA supercomplexes from the cyanobacterium Synechococcus PCC 7942
Spectroscopic properties of PSI-IsiA supercomplexes from the cyanobacterium Synechococcus PCC 7942
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DOI：
10.1016/s0005-2728(02)00371-7
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发表时间：
2002-12-02
影响因子：
4.3
通讯作者：
Dekker, JP
中科院分区：
文献类型：
--
作者：
Andrizhiyevskaya, EG;Schwabe, TME;Dekker, JP
在铁饥饿下生长的蓝细菌聚球藻PCC 7942组装由三聚体光系统I（PSI）复合物组成的超复合物，该复合物被18个CP 43 '或IsiA捕光复合物的环包围[Nature 412（2001）745]。在这里，我们提出了一个光谱表征温度依赖性的吸收和荧光光谱，在5 K的位点选择性荧光光谱，和圆二色性分离的PSI-IsiA，PSI和IsiA复合物从铁饥饿下生长的蓝藻。结果表明，IsiA环增加PSI的吸收截面约100%。每个IsiA亚基结合约16-17个叶绿素a（Chla）分子，并作为PSI的有效天线。三聚体PSI复合物的每个单体含有两个红色叶绿素，这可能会产生一个激子耦合二聚体，并在5 K吸收和荧光在703和713 nm，分别。这些C-703叶绿素的光谱特性不受IsiA天线环存在的影响。纯化的IsiA复合物的光谱性质与植物中相关的CP 43复合物的光谱性质相似，只是在682.5nm处有CP 43的特征窄吸收带。在IsiA失踪了(C)2002 Elsevier Science B. V.保留所有权利。
The cyanobacterium Synechococcus PCC 7942 grown under iron starvation assembles a supercomplex consisting of a trimeric Photosystem I (PSI) complex encircled by a ring of 18 CP43' or IsiA light-harvesting complexes [Nature 412 (2001) 745]. Here we present a spectroscopic characterization by temperature-dependent absorption and fluorescence spectroscopy, site-selective fluorescence spectroscopy at 5 K, and circular dichroism of isolated PSI-IsiA, PSI and IsiA complexes from this cyanobacterium grown under iron starvation. The results suggest that the IsiA ring increases the absorption cross-section of PSI by about 100%. Each IsiA subunit binds about 16-17 chlorophyll a (Chl a) molecules and serves as an efficient antenna for PSI. Each of the monomers of the trimeric PSI complex contains two red chlorophylls, which presumably give rise to one exciton-coupled dimer and at 5 K absorb and fluoresce at 703 and 713 nm, respectively. The spectral properties of these C-703 chlorophylls are not affected by the presence of the IsiA antenna ring. The spectroscopic properties of the purified IsiA complexes are similar to those of the related CP43 complex from plants, except that the characteristic narrow absorption band of CP43 at 682.5 rim. is missing in IsiA. (C) 2002 Elsevier Science B.V. All rights reserved.