Barillà Daniela, Hayes Finbarr
Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology, PO Box 88, Manchester M60 1QD, UK.
Mol Microbiol. 2003 Jul;49(2):487-99. doi: 10.1046/j.1365-2958.2003.03564.x.
The mechanism by which low copy number plasmids are segregated at cell division involves the concerted action of two plasmid-encoded proteins that assemble on a centromere-like site. This study explores the topology of the DNA segregation machinery specified by the parFG locus of TP228, a partition system which is phylogenetically distinct from more well-characterized archetypes. A variety of genetic, biochemical and biophysical strategies revealed that the ParG protein is dimeric. ParF, which is more closely related to the cell division regulator MinD than to the prototypical ParA partition protein of plasmid P1, is instead multimeric and its polymeric state appears to be modulated by ATP which correlates with the proposed ATP-binding activity of ParF. ParG interacts in a sequence-specific manner with the DNA region upstream of the parFG locus and this binding is modulated by ParF. Intriguingly, the ParF and ParG proteins form at least two types of discrete complex in the absence of this region suggesting that the assembly dynamics of these proteins onto DNA is intricate.
低拷贝数质粒在细胞分裂时进行分离的机制涉及两种质粒编码蛋白的协同作用，这两种蛋白会组装在一个类着丝粒位点上。本研究探讨了由TP228的parFG基因座所指定的DNA分离机制的拓扑结构，TP228是一种分区系统，在系统发育上与特征更明确的原型不同。多种遗传、生化和生物物理策略表明，ParG蛋白是二聚体。ParF与细胞分裂调节因子MinD的关系比与质粒P1的典型ParA分区蛋白的关系更为密切，它是多聚体，其聚合状态似乎受ATP调节，这与ParF所提出的ATP结合活性相关。ParG以序列特异性方式与parFG基因座上游的DNA区域相互作用，这种结合受ParF调节。有趣的是，在没有该区域的情况下，ParF和ParG蛋白形成至少两种类型的离散复合物，这表明这些蛋白在DNA上的组装动力学很复杂。
