Formation of oxygen-evolving system of photosynthesis

光合放氧系统是由核蛋白和叶绿体蛋白在光照下协同组装在类囊体膜上而形成的。在本研究中，我们研究了PS-Ⅱ相关蛋白的合成和组装在裸藻细胞和大麦幼苗的绿化过程中。在裸藻，天线叶绿素结合蛋白CP 43/47是不稳定的早期阶段的绿化，我们发现，外部30 kDa的蛋白质PS II的结合是负责CP 43/47的稳定。结果表明，外源性30 kDa蛋白与藻体叶绿素-蛋白复合物紧密相连，并调节藻体叶绿素-蛋白复合物的构象。为了观察30 kDa蛋白质前体的结构，我们进行了该蛋白质的cDNA克隆。该前体具有与高等植物中相应蛋白不同的前序列。叶绿体的包膜，这是负责易位的前体蛋白跨越信封的接触点，通过电子显微镜检查。核编码蛋白质在叶绿体中的运输可能受到由三层膜组成的被膜的限制。

Photosynthetic oxygen-evolving system is organized by the coordinated assembly of the nuclear- and chloroplast-encoded proteins in thylakoid membranes under illumination. In the present study, we investigated synthesis and assembly of the PS-II related proteins in the greening process of Euglena cells and barley seedlings. In Euglena, the antenna chlorophyll-binding proteins CP43/47 are unstable in the early stage of greening, and we found that binding of extrinsic 30 kDa proteins to PS II is responsible for the stabilization of CP43/47. The results suggest that the extrinsic 30 kDa proteins are located closely to the antenna chlorophyll-protein complexes and regulates their conformation.We also studied transport of the 30 kDa protein in Euglena cells. To see the structure of the precursor to the 30 kDa protein, we carried out cDNA cloning of the protein. The precursor had a presequence different from that of the corresponding protein from higher plants. Contact sites of the envelope of chloroplasts, which are responsible for translocation of the precursor proteins across the envelopes, were examined by electron microscopy. It is probable that transport of nuclear-encoded proteins in chloroplasts is limited by the envelopes consisting of triple membranes.