Hunter C N, Pennoyer J D, Niederman R A
Prog Clin Biol Res. 1982;102 Pt B:257-65.
The B875 and B800-850 light-harvesting pigment-protein complexes of Rhodopseudomonas sphaeroides are characterized further by lithium dodecyl sulfate/polyacrylamide gel electrophoresis at 4 degrees C. Bacteriochlorophyll a was shown in reconstruction studies to remain complexed with its respective binding proteins during this procedure. From distributions in these gels, a quantitative description for the arrangement of the complexes is proposed. Assembly of the complexes was examined in delta-aminolevulinate-requiring mutant H-5 after a shift from high- to low-light intensity. After 10 h of delta-[3H]aminolevulinate labeling, the specific radioactivity of bacteriochlorophyll in a fraction containing putative membrane invaginations reached the maximal level, while that of the mature photosynthetic membrane was at only one-third this level. This suggests that membrane invaginations are sites of preferential bacteriochlorophyll synthesis in which completed pigment-proteins exist transiently. Analysis of the 3H distribution after electrophoretic separation further suggests that photosynthetic membranes grow mainly by addition of B800-850 to preformed membrane consisting largely of B875 and photochemical reaction centers. These results corroborate the above model for the structural organization of the light-harvesting system and indicate that the structurally and functionally discrete B800-850 pool is not completely assembled until all B875 sites for B800-850 interactions are occupied.
通过在4℃下进行十二烷基硫酸钠/聚丙烯酰胺凝胶电泳，对球形红假单胞菌的B875和B800 - 850捕光色素 - 蛋白复合物进行了进一步表征。在重建研究中表明，在此过程中细菌叶绿素a与其各自的结合蛋白保持复合状态。根据这些凝胶中的分布情况，提出了复合物排列的定量描述。在从高光强度转变为低光强度后，对需要δ - 氨基乙酰丙酸的突变体H - 5中的复合物组装进行了检查。经过10小时的δ - [³H]氨基乙酰丙酸标记后，含有假定膜内陷的部分中细菌叶绿素的比放射性达到最高水平，而成熟光合膜的比放射性仅为该水平的三分之一。这表明膜内陷是细菌叶绿素优先合成的部位，其中完整的色素 - 蛋白短暂存在。电泳分离后对³H分布的分析进一步表明，光合膜主要通过向主要由B875和光化学反应中心组成的预先形成的膜中添加B800 - 850而生长。这些结果证实了上述捕光系统结构组织模型，并表明在所有用于B800 - 850相互作用的B875位点被占据之前，结构和功能上离散的B800 - 850库并未完全组装。
