Molecular Topology and Development in a Photosynthetic Membrane System

本研究的目的是进一步了解在进化上“原始”的原核生物——绿藻（Chloroflexus aurantiacus）中光合膜系统的结构和功能。其反应中心和光收集天线系统相对简单，使绿藻成为研究光合能量捕获和光合装置遗传调控与组装的良好模型系统。这些实验是先前定义光合装置结构的工作的延续。此外，利用重组DNA技术进行的一系列实验将分离出绿藻光合机构的编码基因。这些分离的基因将用于分析光合机构的结构及其组装调节。近年来遗传技术的发展为研究细菌光合膜组装调控提供了新的途径。这些实验在很大程度上证实了早期工人的观察，即组装对光线和氧气水平有反应。这种控制的确切机制尚不清楚，但很明显，几种光合作用成分受到单独的调节控制。目前的信息显示了三个级别的监管。一种调节机制似乎是绿叶藻光合装置所特有的：翻译后蛋白加工。这一机制可能与调节叶绿体的组装有关。这样的加工机制预示着几个叶绿体多肽被编码在一个单一的信息上，翻译成一个单一的多肽，然后被切割。本项目提出的遗传分析将通过确定编码叶绿体多肽的基因结构，为蛋白质加工假说提供直接测试。

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.