Kerfeld C A, Yeates T O, Thornber J P
Department of Biology, University of California, Los Angeles 90024-1570.
Biochim Biophys Acta. 1994 Apr 28;1185(2):193-202. doi: 10.1016/0005-2728(94)90210-0.
Two complexes, the reaction center light-harvesting complex 1 (RC-LH1) and the B820 subunit of the LH1, have been isolated and characterized from the purple-sulfur photosynthetic bacterium Chromatium purpuratum. The RC-LH1 consists of the B870 antenna and a P-870 RC with an associated tetraheme cytochrome. This complex can be further fractionated to yield the B820 subunit of the LH1. The C. purpuratum B820 subunit is the first isolated from a purple-sulfur bacterium. It is also the first that retains its carotenoid absorption properties. CD spectra in the Qy region of bacteriochlorophyll a in both the RC-LH1 and the B820 subunit are bathochromically shifted as compared to other such complexes. Comparison of the sequence of the LH1 beta polypeptide to other LH1 beta s reveals the presence of additional aromatic amino acids in the vicinity of both of the conserved histidines in the C. purpuratum beta polypeptide. The CD spectra of these C. purpuratum pigment-protein complexes can be interpreted in terms of exciton interaction between bacteriochlorophylls in the B820 subunit of the LH1 and in the B870, with additional spectral characteristics arising from interactions of the pigments with their protein environment.
从紫色硫光合细菌紫硫色杆菌（Chromatium purpuratum）中分离并鉴定了两种复合物，即反应中心光捕获复合物1（RC-LH1）和LH1的B820亚基。RC-LH1由B870天线和带有相关四血红素细胞色素的P-870反应中心组成。该复合物可进一步分级分离以产生LH1的B820亚基。紫硫色杆菌的B820亚基是首次从紫色硫细菌中分离出来的。它也是第一个保留其类胡萝卜素吸收特性的亚基。与其他此类复合物相比，RC-LH1和B820亚基中细菌叶绿素a在Qy区域的圆二色光谱发生了红移。将LH1β多肽的序列与其他LH1β进行比较，发现在紫硫色杆菌β多肽中两个保守组氨酸附近存在额外的芳香族氨基酸。这些紫硫色杆菌色素-蛋白质复合物的圆二色光谱可以根据LH1的B820亚基和B870中细菌叶绿素之间的激子相互作用来解释，色素与其蛋白质环境的相互作用产生了额外的光谱特征。
