REGULATION OF CHLOROPHYLL-APOPROTEIN SYNTHESIS

这项研究的长期目标是确定生物化学机制 调节叶绿素的合成和组装， 脱辅基蛋白 第一个具体目标是阐明D1合成是如何 受叶绿素α和一个核基因的调节， 大麦突变体vir 115。 D1是一种叶绿素脱辅基蛋白， D2结合脱镁叶绿素、叶绿素和醌类。 这种异二聚体形成 光系统II的反应中心，一种介导 叶绿体中的放氧和质体醌还原。 D1没有 在缺乏叶绿素的黑暗生长的植物中积累。 然而，mRNA 编码这种蛋白质与多核糖体和翻译有关 可以在脉冲标记的质体中检测到中间体。 D1累积 当植物被光照并合成叶绿素时。 该数据 表明叶绿素结合将通过进行D1中的步骤来分析 翻译，易位到膜和叶绿素结合将是 通过实现几个具体目标进行分析;（1）D1的早期步骤 翻译将使用足印分析来分析，以鉴定核糖体 结合位点，（2）膜结合D1翻译的性质 将使用脉冲追踪试验研究中间体，确定是否 中间体与多聚核糖体结合， 核糖体在膜多核糖体中发现的psbA mRNA上的分布，（3） 将研究D1向类囊体膜的转运， 研究了转运和叶绿素结合的协调性，（4） 蛋白水解的D1将被检查和核编码的作用， D1合成中蛋白质的鉴定，（5）通过研究获得的知识 D1的分析将扩展到另外三种chl-脱辅基蛋白的分析 (CP47，P700叶绿素脱辅基蛋白）。 此外，蓝色的机制 将研究光调节psbD-psbC RNA群体; 1. 的 转录和RNA稳定性对光诱导的 将定量两种psbD-psbC RNA的积累，2. 因素 将鉴定受刺激psbD-psbC转录; 3. 蓝光 编码调节psbD-的质体蛋白的诱导型核基因 psbC表达将被分离。

The long range goal of this research is to define biochemical mechanisms which regulate the synthesis and assembly of chlorophyll and chlorophyll- apoproteins. The first specific aim is to elucidate how D1 synthesis is regulated by chlorophyll alpha and a nuclear gene which is disrupted in the barley mutant vir115. D1 is a chlorophyll-apoprotein which, together with D2, binds pheophytin, chlorophyll and quinones. This heterodimer forms the reaction center of Photosystem II, a large protein complex which mediates oxygen evolution and plastoquinone reduction in chloroplasts. D1 does not accumulate in dark-grown plants which lack chlorophyll. However, mRNA encoding this protein is associated with polysomes and translation intermediates can be detected in pulse-labeled etioplasts. D1 accumulates when plants are illuminated and chlorophyll is synthesized. This data suggests that chlorophyll binding will be analyzed by carrying steps in D1 translation, translocation into membranes and chlorophyll binding will be analyzed by carrying out several specific objectives; (1) Early steps in D1 translation will be analyzed using toeprint assays to identify ribosome binding sites, (2) The nature of membrane bound D1 translation intermediates will be investigated using pulse-chase assays, determining if the intermediates are associated with polysomes and by determining the distribution of ribosomes on psbA mRNA found in membrane polysomes, (3) Translocation of D1 into thylakoid membranes will be studied and the coordination of translocation and chlorophyll-binding investigated, (4) Proteolysis of D1 will be examined and the role of a nuclear encoded protein in D1 synthesis identified, (5) Knowledge gained through the study of D1 will be extended to the analysis of three additional chl-apoproteins (CP47, P700 chl-apoproteins). In addition, the mechanisms by which blue light regulates the psbD-psbC RNA population will be studied; 1. The influence of transcription and RNA stability on the light-induced accumulation of two psbD-psbC RNAs will be quantitated, 2. Factors which stimulate psbD-psbC transcription will be identified and 3. Blue light inducible nuclear genes which encode the plastid proteins regulating psbD- psbC expression will be isolated.