STRUCTURE & EVOLUTION OF PLANT PHOTORECEPTOR PHYTOCHROME

环境光感知对最佳生长至关重要， 植物的发展。 在自然环境中，植物暴露在 极端的光强度和光谱质量，因此必须 不断优化光合作用的光捕获。 这是 通过光敏色素的作用完成，光敏色素是一种分子光传感器， 其作用是调节基因表达、生长 速率或叶绿体定向。 最近的鉴定和 集胞藻光敏色素基因的克隆 我实验室的PCC 6803提供了关于 光感受器的结构，从已知的最简单的生物体， 拥有它。DNA和蛋白质序列比较超过25 全长光敏色素有相当大的扩展模型， 这种重要植物结构、功能和进化 光感受器 我们正在进行的研究将导致新的信息， 光敏色素分子不同结构域的祖先起源 并深入了解这种生物化学功能的进化， 光感受器家族 首先，我们计划进一步评估 大约250个氨基酸的直接重复序列， 包括光敏色素的C-末端，细菌传感器蛋白 和其他真核生物蛋白质同源物。 这将是完成 使用PROFILESS和PROFILEMAKE来识别整个超家族 蛋白质，其表现出双重的“transmitter样”激酶结构域。 使用程序对该超家族进行多序列比对 MSA、CLUSTAL和佐贺将使我们能够进一步定义这种新的 “主题”。 这些信息是确定 不同家庭成员之间的系统发育关系， 菲利普。 第二，我们将执行递归Profile编译， 细菌的各种成员的多重序列比对 受体家族，以确定共同的结构基序， orf 2是蓝藻光敏色素的潜在底物 S6803phy1. 这些信息应该有助于识别和 克隆与植物光敏色素相互作用的分子， PCR，或通过它们在植物EST数据库中的鉴定。 在 此外，orf 2和cheY的同源建模， 结构已知，将启动。 第三，我们将确定 光敏色素“感光结构域”的其他同系物， 我们的肽谱。 在 通过这种方式，我们希望在物种中识别这个家族的新成员， 目前认为缺乏光敏色素的植物（如酵母、昆虫和 哺乳动物）。 我们还将确定潜在的同系物的 光敏色素感光体的发色团结合结构域。 这 信息应该扩展我们对进化的理解， 可能是这个重要的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 在差异而不是相似性方面的一致性。 这 一种类型的分析可以提供新的线索， 光敏色素的“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.