SMALL ANGLE X-RAY SCATTERING OF CIRCADIAN CLOCK PROTEIN COMPLEX

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。生物钟是自我维持的生化振荡器。它们的特性包括温度补偿、约24小时的时间常数和高精度（Dunlap等人，2004年）。这些性质很难用已知的生物化学反应来解释。对这些不寻常的振荡器的机制的最终解释将需要描述生物钟的分子组成部分的结构，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，其中遗传/生物化学研究已经取得成效（Ishiura et al. 1998，Nakahira et al. 2004和Johnson 2004）。 蓝藻生物钟系统的一个有趣的特征是全局基因调控--基本上所有的启动子都在生物钟的控制之下。甚至异源启动子也被有节奏地引入蓝细菌中表达（Nakahira等人，2004）。突变分析发现，该系统由至少三种必需的时钟基因kaiA、kaiB和kaiC调节，所述基因在染色体上形成簇（Ishiura et al.，1998年）。由这些基因编码的蛋白质彼此相互作用（Iwasaki et al.1999和Taniguchi et al.2001）以在体内形成大的复合物，其中KaiC是六聚体核心。KaiC的晶体结构（Pattanayek等人，2003年），KaiA和KaiB被不同的群体所知。 我们建议通过小角X射线散射来分析时钟蛋白KaiA，KaiB和KaiC在溶液中的相互作用。

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.