Vecchiarelli Anthony G, Seol Yeonee, Neuman Keir C, Mizuuchi Kiyoshi
a Laboratory of Molecular Biology ; National Institute of Diabetes and Digestive and Kidney Diseases; National Institutes of Health ; Bethesda , MD USA.
Bioarchitecture. 2014;4(4-5):154-9. doi: 10.4161/19490992.2014.987581.
DNA segregation is a critical process for all life, and although there is a relatively good understanding of eukaryotic mitosis, the mechanism in bacteria remains unclear. The small size of a bacterial cell and the number of factors involved in its subcellular organization make it difficult to study individual systems under controlled conditions in vivo. We developed a cell-free technique to reconstitute and visualize bacterial ParA-mediated segregation systems. Our studies provide direct evidence for a mode of transport that does not use a classical cytoskeletal filament or motor protein. Instead, we demonstrate that ParA-type DNA segregation systems can establish a propagating ParA ATPase gradient on the nucleoid surface, which generates the force required for the directed movement of spatially confined cargoes, such as plasmids or large organelles, and distributes multiple cargos equidistant to each other inside cells. Here we present the critical principles of our diffusion-ratchet model of ParA-mediated transport and expand on the mathematically derived chemophoresis force using experimentally-determined biochemical and cellular parameters.
DNA分离是所有生命的关键过程，尽管对真核细胞有丝分裂有了相对较好的理解，但细菌中的机制仍不清楚。细菌细胞的小尺寸及其亚细胞组织中涉及的多种因素使得在体内可控条件下研究单个系统变得困难。我们开发了一种无细胞技术来重组和可视化细菌ParA介导的分离系统。我们的研究为一种不使用经典细胞骨架丝或运动蛋白的运输模式提供了直接证据。相反，我们证明ParA型DNA分离系统可以在类核表面建立一个传播的ParA ATP酶梯度，该梯度产生空间受限货物（如质粒或大型细胞器）定向移动所需的力，并在细胞内将多个货物彼此等距分布。在这里，我们介绍了我们的ParA介导运输的扩散棘轮模型的关键原理，并使用实验确定的生化和细胞参数扩展了数学推导的化学驱动力。
