STRUCTURE & EVOLUTION OF PLANT PHOTORECEPTOR PHYTOCHROME

环境光感知对于最佳生长和 植物的发育。 在自然环境中，植物裸露在外 光强度和光谱质量达到极端，因此必须 不断优化光合作用的光捕获。 这是 通过光敏色素（一种分子光传感器）的作用来完成 它有助于介导基因表达、生长的适应性变化 速率或叶绿体方向。 最近的鉴定和 蓝藻集胞藻光敏色素的克隆 我的实验室中的 PCC6803 提供了有关 已知最简单的生物体的感光体结构 拥有它。 DNA 和蛋白质序列与超过 25 个的比较 全长光敏色素具有相当大的扩展模型 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 光敏色素分子不同域的祖先起源 并深入了解这种生物化学功能的演变 光感受器家族。 首先，我们计划进一步评估 大约 250 个氨基酸同向重复序列的重要性 包含光敏色素（细菌传感器蛋白）的 C 末端 和其他真核蛋白质同系物。 这将实现 使用 PROFILESS 和 PROFILEMAKE 来识别整个超家族 蛋白质，表现出双重“递质样”激酶结构域。 使用该程序对该超家族进行多序列比对 MSA、CLUSTAL 和 SAGA 将使我们能够进一步定义这一新的 “主题”。 该信息是确定的先决条件 不同家族成员之间的系统发育关系 菲利普。 其次，我们将执行递归配置文件搜索和 细菌不同成员的多重序列比对 接收者家族，以识别共同的结构基序 orf2，蓝藻光敏色素的潜在“底物” S6803phy1。 该信息应该有助于识别和 克隆分子，通过以下方式与植物中的光敏色素相互作用 PCR，或通过植物 EST 数据库中的鉴定。 在 另外，orf2和cheY的同源建模，其中一个晶体 结构已知，将被启动。 第三，我们要确定 光敏色素“光感域”的其他同系物，通过添加 我们的肽谱中包含该家族的蓝藻成员。 在 通过这种方式，我们希望能够在物种中识别出这个家族的新成员 迄今为止，人们认为缺乏光敏色素（例如酵母、昆虫和 哺乳动物）。 我们还将鉴定潜在的同系物 光敏色素感光体的发色团结合域。 这个 信息应该扩展我们对进化的理解 可能是这种重要光感受器的生化功能。 第四，我们建议分析光敏色素蛋白序列 对齐是根据差异而不是相似之处。 这个 类型的分析可以为赋予区域的新线索 光敏色素“物种特异性”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.