Molecular Topology and Development in a Photosynthetic Membrane System

本研究的目的是为了进一步了解进化上“原始”的原核生物--橙绿线虫光合膜系统的结构和功能。Chlorofleus的反应中心和捕光天线系统相对简单，是研究光合作用能量捕获及其光合器遗传调控和组装的优秀模型系统。这些实验是之前定义光合作用装置结构的工作的继续。此外，应用重组DNA技术的一系列实验将分离编码绿藻光合作用装置的基因。这些分离的基因将被用来分析光合作用装置的结构及其组装的调节。最近发展起来的基因技术的应用为研究细菌光合膜组装的调控提供了新的方法。这样的实验在很大程度上证实了早期工作人员的观察结果，即组装对光和氧气水平做出反应。这种控制的确切机制尚未阐明，但很明显，几个光合作用成分受到单独的调控。目前的信息表明，监管有三个层面。有一种调节机制似乎是叶绿藻光合作用装置所独有的：翻译后蛋白质加工。这一机制可能参与了对绿小体组装的调控。这样的处理机制预测，几个绿体多肽被编码在单个消息上，翻译成单个多肽，然后被切割。这个项目中提出的遗传分析将通过确定编码绿小体多肽的基因的结构来直接检验蛋白质加工假说。

The objective of this research is to further the understanding of the structure and function of the photosynthetic membrane system in the evolutionarily "primitive" prokaryote, Chloroflexus aurantiacus. The relative simplicity of its reaction center and light- harvesting antenna systems make Chloroflexus an excellent model system for the study of photosynthetic energy capture and the genetic regulation and assembly of its photosynthetic apparatus. These experiments are a continuation of previous work defining the architecture of the photosynthetic apparatus. In addition, a series of experiments applying recombinant DNA techniques will isolate genes encoding the photosynthetic apparatus in Chloroflexus. These isolated genes will be used for analyzing both the structure of the photosynthetic apparatus and its regulation of assembly. Application of recently developed genetic techniques has resulted in new approaches for studying regulation of assembly of bacterial photosynthetic membranes. Such experiments have largely confirmed the observations of earlier workers, in that assembly responds to light and oxygen levels. The exact mechanisms for this control have not yet been clarified, but it is clear that several photosynthetic components are under separate regulatory control. Current information indicates three levels of regulation. One regulatory mechanism appears unique to the Chloroflexus photosynthetic apparatus: post-translational protein processing. This mechanism may be involved in regulation of chlorosome assembly. Such a processing mechanism predicts that the several chlorosome polypeptides are encoded on a single message, translated into a single polypeptide, then cleaved. The genetic analysis proposed in this project will provide a direct test of the protein- processing hypothesis by determining the structure of the genes encoding the chlorosome polypeptides.