The molecular events that underpin genome segregation during bacterial cytokinesis have not been fully described. The tripartite segrosome complex that is encoded by the multiresistance plasmid TP228 in Escherichia coli is a tractable model to decipher the steps that mediate accurate genome partitioning in bacteria. In this case, a “Venus flytrap” mechanism mediates plasmid segregation. The ParG sequence-specific DNA binding protein coats the parH centromere. ParF, a ParA-type ATPase protein, assembles in a three-dimensional meshwork that penetrates the nucleoid volume where it recognizes and transports ParG-parH complexes and attached plasmids to the nucleoid poles. Plasmids are deposited at the nucleoid poles following the partial dissolution of the ParF network through a combination of localized ATP hydrolysis within the meshwork and ParG-mediated oligomer disassembly. The current study demonstrates that the conformation of the nucleotide binding pocket in ParF is tuned exquisitely: a single amino acid change that perturbs the molecular arrangement of the bound nucleotide moderates ATP hydrolysis. Moreover, this alteration also affects critical interactions of ParF with the partner protein ParG. As a result, plasmid segregation is inhibited. The data reinforce that the dynamics of nucleotide binding and hydrolysis by ParA-type proteins are key to accurate genome segregation in bacteria.

细菌胞质分裂过程中支持基因组分离的分子事件尚未完全描述。由多抗性质粒TP228编码的三方脂质体复合物大肠杆菌是一种易于处理的模型，可用来解释介导细菌中准确的基因组分配的步骤。在这种情况下，“维纳斯捕蝇器”机制介导质粒分离。ParG序列特异性DNA结合蛋白可包裹帕尔着丝粒。ParF是一种Pa​​rA型ATPase蛋白，它组装在一个三维网状结构中，该网状结构穿透了可识别和转运ParG-帕尔复合体和连接质粒的核苷极。通过将网状结构内的局部ATP水解和ParG介导的低聚物分解相结合，将ParF网络部分溶解后，质粒便会沉积在核苷极处。当前的研究表明，ParF中核苷酸结合口袋的构象可以精确调节：单个氨基酸变化会干扰结合核苷酸的分子排列，从而促进ATP水解。而且，这种改变也影响ParF与伴侣蛋白ParG的关键相互作用。结果，质粒分离被抑制。数据表明，ParA型蛋白的核苷酸结合和水解动力学是细菌中精确的基因组分离的关键。