Formation of oxygen-evolving system of photosynthesis

光合进化氧系统是在光照下由核编码蛋白和叶绿体编码蛋白在类囊体膜内协调组装而成的。在本研究中，我们研究了PS-II相关蛋白在绿绿细胞和大麦幼苗变绿过程中的合成和组装。在绿藻中，天线叶绿素结合蛋白CP43/47在绿化初期是不稳定的，我们发现外源的30kda蛋白与PS II的结合是CP43/47稳定的原因。结果表明，外源性30kda蛋白位于天线叶绿素-蛋白复合物附近，并调节其构象。我们还研究了30 kDa蛋白在Euglena细胞中的转运。为了了解30kda蛋白前体的结构，我们对该蛋白进行了cDNA克隆。该前体具有与高等植物中相应蛋白质不同的前体序列。叶绿体包膜的接触位点负责前体蛋白在包膜上的易位，用电子显微镜检查。叶绿体中核编码蛋白的运输可能受到由三层膜组成的包膜的限制。

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.