SOLUTION X-RAY SCATTERING STUDIES ON P1 PARTITION COMPLEXES

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 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。这一过程被称为分割或分离，是由功能上同源的PAR系统介导的，该系统由一个顺式作用的着丝粒样DNA位点(S)和两个蛋白质ParA和PARB组成。大肠埃希氏菌P1质粒分割仪已被用作分割器的范例。P1para是一个44 kDa的Walker类型的ATPase，它驱动着最后一步的分离。P1PARB是一个38 kDa的DNA结合蛋白，在分离、分配复合体形成和配对的初始步骤中起中介作用。在配位复合体的形成过程中，PARB与大肠杆菌蛋白整合宿主因子(IHF)协同结合到74bp的PARS着丝粒样位点，含有多个A-盒和B-盒。虽然P1PAR系统已经被很好地描述了，但由于缺乏关于分配蛋白及其复合体的结构信息，对分配的详细机制缺乏了解。我们试图通过溶液x射线散射获得这些组分的络合物的三维结构，以了解分配的分子机理。基于已有的PARB-IHF-PARS配位络合物的高分辨结构，我们构建了截断的PARB-IHF-PARS配位络合物的结构模型。我们的目标是首先通过溶液X射线散射来验证该模型，然后进一步建立包含全长PARB和不同类型的PARS的较大分配络合物的三维结构模型，最终得到预分离复合体PARB-IHF-PARS(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.