SMALL ANGLE X-RAY SCATTERING OF CIRCADIAN CLOCK PROTEIN COMPLEX

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。生物钟是自我维持的生化振荡器。其特性包括温度补偿，时间常数约为24小时，精度高（Dunlap et al., 2004）。这些性质很难用已知的生化反应来解释。对这些不寻常的振荡机制的最终解释将需要表征昼夜节律钟的分子成分的结构、功能和相互作用。我们建议了解原核蓝藻中生物钟的组成部分，遗传/生化研究已经取得了成果（Ishiura et al. 1998, Nakahira et al. 2004和Johnson2004）。蓝藻生物钟系统的一个有趣特征是全球基因调控——基本上生物体中的所有启动子都受昼夜节律控制。甚至异源启动子也有节奏地表达到蓝藻中（Nakahira et al. 2004）。一项突变分析发现，该系统受到至少三个基本时钟基因kaiA、kaiB和kaiC的调控，它们在染色体上形成一个簇（Ishiura et al., 1998）。这些基因编码的蛋白质相互作用（Iwasaki et al. 1999和Taniguchi et al. 2001），在体内形成以KaiC为六聚体核心的大型复合物。KaiC （Pattanayek et al., 2003）、KaiA和KaiB的晶体结构为不同的类群所知。我们提出通过小角x射线散射分析溶液中时钟蛋白KaiA、KaiB和KaiC之间的相互作用。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Circadian clocks are self-sustained biochemical oscillators. Their properties include temperature compensation, a time constant of approximately 24 hr, and high precision (Dunlap et al., 2004). These properties are difficult to explain by known biochemical reactions. The ultimate explanation for the mechanism of these unusual oscillators will require characterizing the structures, functions, and interactions of the molecular components of circadian clocks. We propose to understand the components of the biological clock in the prokaryotic cyanobacteria, where genetic/biochemical studies have been productive (Ishiura et al. 1998, Nakahira et al. 2004 and Johnson2004). An intriguing feature of the circadian clock system of cyanobacteria is that of global gene regulation-essentially all the promoters in the organism are under circadian control. Even heterologous promoters are expressed rhythmically introduced into cyanobacteria (Nakahira et al. 2004). A mutational analysis discovered that this system is regulated by at least three essential clock genes, kaiA, kaiB, and kaiC, that form a cluster on the chromosome (Ishiura et al., 1998). The proteins encoded by these genes interact with each other (Iwasaki et al. 1999 and Taniguchi et al. 2001) to form large complexes in vivo in which KaiC is the hexameric core. The crystal structure of the KaiC (Pattanayek et al., 2003),KaiA and KaiB are known by different groups. We propose to analyze interactions among the clock proteins KaiA, KaiB, and KaiC in solution through small angle X-ray scattering.