SOLUTION X-RAY SCATTERING STUDIES ON P1 PARTITION COMPLEXES

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。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。列出的机构是 中心，不一定是研究者的机构。 原核遗传物质的忠实遗传需要染色体和质粒在细胞分裂时定向移动和定位到子细胞。 该过程称为分配或分离，由功能同源的par系统介导，par系统由顺式作用的着丝粒样DNA位点和两种蛋白质帕拉和ParB组成。 大肠杆菌P1质粒分配装置已用作分配的范例。 P1帕拉是一个44 kDa的步行者型ATP酶，在最后一步的分配中驱动质粒分离。P1 ParB是一种38 kDa的DNA结合蛋白，介导分离的初始步骤;分区复合物的形成和配对。 ParB和E.大肠杆菌蛋白整合宿主因子（IHF）与含有多个A盒和B盒的parS着丝粒样位点（~74 bp）协同结合形成分配复合物。虽然P1 Par系统已被生物化学表征，但缺乏对分区的详细机制理解，这在很大程度上是由于缺乏分区蛋白及其复合物的结构信息。我们试图通过溶液X射线散射获得这些组分的复合物的三维结构，以了解分配的分子机制。我们已经构建了一个结构模型的截断ParB-IHF-parS分区复合物，根据其组件的可用的高分辨率结构。我们的目标是首先通过溶液X射线散射验证该模型，并进一步构建涉及全长ParB和不同类型的parS的较大分区复合物的三维结构模型，最终构建预分离复合物ParB-IHF-帕拉（ATP）-parS。

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. The faithful inheritance of prokaryotic genetic material requires the directed movement and positioning of chromosomes and plasmids to daughter cells at cell division. This process, called partition or segregation, is mediated by functionally homologous par systems comprised of a cis-acting centromere-like DNA site(s) and two proteins, ParA and ParB. The Escherichia coli P1 plasmid partition apparatus has served as a paradigm for partition. P1 ParA is a 44 kDa Walker type ATPase that drives plasmid separation at the final step of partition. P1 ParB is a 38 kDa DNA-binding protein that mediates the initial steps in segregation; partition complex formation and pairing. In partition complex formation, ParB and the E. coli protein, integration host factor (IHF), bind cooperatively to the ~74 bp parS centromere-like site, which contains multiple A- and B-Boxes, to form the partition complex. Although the P1 Par system has been biochemically well characterized, a detailed mechanistic understanding of partition is lacking due, in large part, to the dearth of structural information on partition proteins and their complexes. We attempt to obtain three dimensional structures of the complexes of these components by solution x-ray scattering to understand molecular mechanism of partition. We have constructed a structural model of the truncated ParB-IHF-parS partition complex, based on the available high resolution structures of its components. Our goals are to first verify that model by solution x-ray scattering, and further build three-dimensional structural models of larger partition complexes involving full length ParB and different types of parS, eventually the pre-segregation complex ParB-IHF-ParA(ATP)-parS.