UNEXPECTED SIMILARITIES OF THE B800-850 LIGHT-HARVESTING COMPLEX FROM RHODOSPIRILLUM-MOLISCHIANUM TO THE B870 LIGHT-HARVESTING COMPLEXES FROM OTHER PURPLE PHOTOSYNTHETIC BACTERIA
UNEXPECTED SIMILARITIES OF THE B800-850 LIGHT-HARVESTING COMPLEX FROM RHODOSPIRILLUM-MOLISCHIANUM TO THE B870 LIGHT-HARVESTING COMPLEXES FROM OTHER PURPLE PHOTOSYNTHETIC BACTERIA
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DOI：
10.1021/bi00072a017
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发表时间：
1993-06-01
期刊：
影响因子：
2.9
通讯作者：
MICHEL, H
中科院分区：
文献类型：
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作者：
GERMEROTH, L;LOTTSPEICH, F;MICHEL, H
利用分子筛和离子交换层析技术，从红螺菌DSM 119的光合膜中分离得到B800-850捕光复合体(又称LH2)。用反相高效液相色谱系统对其两个细菌-叶绿素a结合多肽(α-亚基和β-亚基)进行纯化。测定了这两个亚基的完整氨基酸序列。α和β亚基分别由56和45个氨基酸组成，相对分子质量分别为5939和5133。与来自其他光合细菌的B800-850复合体相反，天然的B800-850复合体来自R.Molischianum最有可能是一种八聚体单体，其化学计量比为每个α，β亚基含有三个细菌叶绿素a和1.5个番茄红素。共振拉曼光谱提供了BCHL中以5配位的镁离子和以全反式构型为主的类胡萝卜素的证据。不同光合细菌的共振拉曼光谱数据的比较表明，B800-850复合体的BCHLA-a结合部位来自Rs。Molischianum更类似于B870复合体(也称为LH1)，而不是其他光合细菌的B800-850复合体。序列相似性，特别是在Rs的B800-850复合体的β-亚基之间。Molischianum和其他光合细菌的B870和B800-850复合体与这一结果一致，并提供了关于细菌天线复合体中色素结合模式的信息。
The B800-850 light-harvesting complex (also called LH2) was isolated from photosynthetic membranes of Rhodospirillum molischianum DSM 119 using molecular sieve and ion-exchange chromatography. Its two bacteriochlorophyll a-binding polypeptides (alpha-subunit and beta-subunit) were purified with a reverse-phase HPLC system. The complete amino acid sequences of both subunits have been determined. The alpha- and beta-subunits consist of 56 and 45 amino acids, respectively, corresponding to molecular weights of 5939 and 5133. In contrast to the B800-850 complexes from other photosynthetic bacteria, the native B800-850 complex from Rs. molischianum is most likely an octamer of monomers with a stoichiometry of three bacteriochlorophyll a and 1.5 lycopenes per alpha,beta-subunit. Resonance Raman spectra provide evidence for a 5-coordinated Mg2+ in the BChl, and a carotenoid mainly in the all-trans configuration. A comparison between resonance Raman data from different photosynthetic bacteria indicates that the BChl a-binding site of the B800-850 complex from Rs. molischianum is more similar to the B870 complexes (also called LH1) than to the B800-850 complexes of other photosynthetic bacteria. Sequence similarities especially between the beta-subunits of the B800-850 complex of Rs. molischianum and the B870 and B800-850 complexes of other photosynthetic bacteria agree with this result and provide information on the mode of pigment binding in bacterial antenna complexes.