Trapping of an assembly intermediate of photosynthetic LH1 antenna beyond B820 subunit
Trapping of an assembly intermediate of photosynthetic LH1 antenna beyond B820 subunit
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DOI：
10.1074/jbc.m501212200
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发表时间：
2005-06-03
影响因子：
4.8
通讯作者：
Scheer, H
中科院分区：
文献类型：
--
作者：
Fiedor, L;Scheer, H
大多数光合作用的LH1触角经历解离成B820亚基，这表明它们作为结构模块的普遍特征。然而，亚基的解离似乎只有在没有类胡萝卜素的情况下才会可逆地发生，而且从未发现亚基与类胡萝卜素结合。类胡萝卜素与B820的相互作用已在一种新发展的红色红螺菌LH1天线的重建实验中进行了研究(Fiedor，L.，Akahane，J.，and Koyama，Y.(2004年)生化43,16487-16496)。这些模型研究表明，B820亚基与类胡萝卜素强烈相互作用，并自发形成具有亚化学计量比类胡萝卜素含量的稳定的类LH1复合体。这是首次有实验证据表明B820可能在体内LH1的组装过程中作为一个短暂的中间体出现。根据离子交换层析和可重复的色素组成，得到的B820亚基与类胡萝卜素的复合体，称为iB873，是均一的。IB873结合的类胡萝卜素与天然天线中的类胡萝卜素一样能有效地将能量传递给细菌-叶绿素。据我们所知，iB873是第一个复杂的结合功能类胡萝卜素，其光谱和生化性质介于B820和完全组装的LH1之间。
Most photosynthetic LH1 antennae undergo dissociation into B820 subunits, suggesting their universal character as structural modules. However, dissociation into subunits seems to occur reversibly only in the absence of carotenoids and the subunits were never found to bind carotenoids. The interactions of carotenoids with B820 have been studied in a newly developed reconstitution assay of the LH1 antenna from Rhodospirillum rubrum (Fiedor, L., Akahane, J., and Koyama, Y. ( 2004) Biochemistry 43, 16487 - 16496). These model studies show that B820 subunits strongly interact with carotenoids and spontaneously form stable LH1-like complexes with substoichiometric carotenoid content. This is the first experimental evidence that B820 may occur as a short-lived intermediate in the assembly of LH1 in vivo. The resulting complex of B820 subunits with carotenoid, termed iB873, is homogeneous, according to ion exchange chromatography and reproducible pigment composition. The iB873-bound carotenoid is as efficient in energy transfer to bacteriochlorophyll as the one in native antenna. To our knowledge, iB873 is the first complex binding functional carotenoid, with the spectral and biochemical properties intermediate between that of B820 and the fully assembled LH1.