Recombinant Lhca2 and Lhca3 subunits of the photosystem I antenna system
Recombinant Lhca2 and Lhca3 subunits of the photosystem I antenna system
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DOI：
10.1021/bi027398r
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发表时间：
2003-04-15
期刊：
影响因子：
2.9
通讯作者：
Croce, R
中科院分区：
文献类型：
--
作者：
Castelletti, S;Morosinotto, T;Croce, R
在这项研究中，两个基因产物（Lhca 2和Lhca 3），编码高等植物（拟南芥）光系统I天线复合物，在细菌中过表达和重组纯化的叶绿体色素在体外。通过生化和光谱方法对由此获得的叶绿素-叶黄素蛋白进行了表征。两种复合物显示每个多肽结合10个叶绿素（a和B）分子，Lhca 2与Lhca 3相比具有更高的叶绿素B含量。这两种蛋白质不同的类胡萝卜素结合位点的数量：两个和三个Lhca 2和Lhca 3，分别。β-胡萝卜素除了与叶黄素、紫黄质和叶黄素特异性结合外，还与Lhca 3特异性结合，这表明该蛋白质中类胡萝卜素结合位点的特殊结构，因为它是迄今为止唯一被鉴定具有结合β-胡萝卜素能力的蛋白质。两种色素蛋白的光谱特性分析表明，在这两种复合物中存在低能量吸收形式（红色形式），尽管具有不同的能量和振幅。Lhca 2在77 K时的荧光发射峰位于701 nm，而Lhca 3的主要发射峰位于725 nm。没有Chl B的Lhca 3的重建揭示了Chl B不参与该复合物的低能量吸收形式的起源。目前的数据进行了讨论，在比较的重组Lhca 1和Lhca 4复合物和天然LHCI制剂，以前分析的性质，从而显示了一个全面的描述的基因产物组成的光系统I光捕获系统的A。thaliana.
In this study, two gene products (Lhca2 and Lhca3), encoding higher plants (Arabidopsis thaliana) Photosystem I antenna complexes, were overexpressed in bacteria and reconstituted in vitro with purified chloroplast pigments. The chlorophyll-xanthophyll proteins thus obtained were characterized by biochemical and spectroscopic methods. Both complexes were shown to bind 10 chlorophyll (a and b) molecules per polypeptide, Lhca2 having higher chlorophyll b content as compared to Lhca3. The two proteins differed for the number of carotenoid binding sites: two and three for Lhca2 and Lhca3, respectively. beta-carotene was specifically bound to Lhca3 in addition to the xanthophylls violaxanthin and lutein, indicating a peculiar structure of carotenoid binding sites in this protein since it is the only one so far identified with the ability of binding beta-carotene. Analysis of the spectroscopic properties of the two pigment proteins showed the presence of low energy absorption forms (red forms) in both complexes, albeit with different energies and amplitudes. The fluorescence emission maximum at 77 K of Lhca2 was found at 701 nm, while in Lhca3 the major emission was at 725 nm. Reconstitution of Lhca3 without Chl b reveals that Chl b is not involved in originating the low energy absorption forms of this complex. The present data are discussed in comparison to the properties of the recombinant Lhca1 and Lhca4 complexes and of the native LHCI preparation, previously analyzed, thus showing a comprehensive description of the gene products composing the Photosystem I light harvesting system of A. thaliana.