STRUCTURE & EVOLUTION OF PLANT PHOTORECEPTOR PHYTOCHROME

环境光感知对最佳生长和 植物的发育。在自然环境中，植物暴露在 在光强度和光谱质量上达到极端，因此必须 持续优化光合作用的光捕获。这是 通过分子光传感器光敏色素的作用完成 它用于调节基因表达、生长的适应性变化 速率或叶绿体取向。最近的身份证明和 集胞蓝藻光敏色素的克隆 我实验室的PCC6803提供了关于 光感受器的结构来自已知的最简单的生物体 拥有它。DNA和蛋白质序列与超过25个 全长光致变色剂在很大程度上扩展了 这种重要植物的结构、功能和进化 光感受器。我们正在进行的研究将带来关于 光敏色素分子不同结构域的起源 以及对这一生化功能的演变的洞察 光感受器家族。首先，我们计划进一步评估 约250个氨基酸直接重复序列的意义 包括光敏色素的C末端，细菌感受器蛋白 和其他真核蛋白质的同源物。这将会实现的 使用PROFILESS和PROFILEMAKE识别整个超家族 蛋白质，它显示一个双重的‘类传递物’的激动域。 使用程序对这个超家族的多个序列进行比对 MSA、CLUSTAL和SAGA将使我们能够进一步定义这一新的 ‘Motif’这些信息是确定 不同家族成员间的亲缘关系 菲力普。其次，我们将执行递归配置文件搜索和 细菌不同成员的多个序列比对 接收器家族，以便识别共同的结构基序 蓝藻光敏色素潜在的“底物”ORF2 S6803Phy1。这一信息应有助于识别和 克隆与植物光敏色素相互作用的分子 或通过它们在植物EST数据库中的鉴定。在……里面 此外，ORF2和Chey的同源模拟，对于该晶体 结构是已知的，将被启动。第三，我们将确定 通过添加光敏色素的光敏结构域的其他同系物 这个家族的蓝藻成员与我们的多肽图谱一致。在……里面 通过这种方式，我们希望在物种上识别这个家族的新成员 迄今为止被认为缺乏光敏色素(例如酵母、昆虫和 哺乳动物)。我们还将确定潜在的同源物 光敏色素感光器的生色团结合域。这 信息应该扩展我们对进化的理解 可能是这种重要的光感受器的生化功能。 第四，我们对光敏色素蛋白序列进行了分析。 在不同而不是相似的方面进行比对。这 分析类型可以提供有关区域的新线索 光敏色素具有“物种特有”的功能。

Environmental photoperception is essential to optimal growth and development of plants. In the natural environment, plants are exposed to extremes in light intensity and spectral quality and therefore must continuously optimize light capture for photosynthesis. This is accomplished by the action of phytochrome, a molecular light sensor which serves to mediate adaptive changes in gene expression, growth rate or chloroplast orientation. The recent identification and cloning of phytochrome from the cyanobacterium Synechocystis sp PCC6803 in my laboratory provides invaluable information on the structure of the photoreceptor from the simplest organism known to possess it. DNA and protein sequence comparisons with more than 25 full-length phytochromes have considerably extended models of the structure, function and evolution of this important plant photoreceptor. Our ongoing studies will lead to new information about the ancestral origin of different domains of the phytochrome mol ecule and insight into the evolution of biochemical function of this photoreceptor family. Firstly, we plan to further evaluate the significance of the roughly 250 amino acid direct repeats which comprise the C-terminus of phytochromes, the bacterial sensor proteins and the other eukaryotic protein homologs. This will be accomplished using PROFILESS and PROFILEMAKE to identify the entire superfamily of proteins, which exhibit a dual 'transmitter-like' kinase domain. Multiple sequence alignments of this superfamily using the programs MSA, CLUSTAL and SAGA will enable us to further define this new 'motif'. This information is a prerequisite for determining phylogenetic relationships between different family members with PHYLIP. Secondly, we will perform recursive Profile Searches and multiple sequence alignments of the various members of the bacterial receiver family in order to identify common structural motifs with orf2, the potential 'substrate' of the cyanobacterial phytochrome S6803phy1. This information should be useful for identification and cloning of molecules, which interact with phytochrome in plants by PCR, or through their identification in the plant EST databases. In addition, homology modeling of orf2 and cheY, for which a crystal structure is known, will be initiated. Thirdly, we will identify other homologs of the 'photosensory domain' of phytochrome by adding cyanobacterial members of this family to our peptide profiles. In this way, we hope to identify new members of this family in species hithertofore thought to lack phytochromes (e.g. yeast, insects and mammals). We will also identify potential homologs of the chromophore-binding domain of the phytochrome photoreceptor. This information should extend our understanding of the evolution and possibly biochemical function of this important photoreceptor. Fourthly, we propose to analyze the phytochrome protein sequence alignments in terms of differences rather than similarities. This type of analysis could provide new clues into regions that confer phytochrome "species-specific" functions.