Bouet Jean-Yves, Ah-Seng Yoan, Benmeradi Nacer, Lane David
Laboratoire de Microbiologie et de Génétique Moléculaire, UMR5100 CNRS, Toulouse, France.
Mol Microbiol. 2007 Jan;63(2):468-81. doi: 10.1111/j.1365-2958.2006.05537.x. Epub 2006 Dec 11.
In bacteria, mitotic stability of plasmids and many chromosomes depends on replicon-specific systems which comprise a centromere, a centromere-binding protein and an ATPase. Dynamic self-assembly of the ATPase appears to enable active partition of replicon copies into cell-halves, but for most ATPases (the Walker-box type) the mechanism is unknown. Also unknown is how the host cell contributes to partition. We have examined the effects of non-sequence-specific DNA on in vitro self-assembly of the SopA partition ATPase of plasmid F. SopA underwent polymerization provided ATP was present. DNA inhibited this polymerization and caused breakdown of pre-formed polymers. Centromere-binding protein SopB counteracted DNA-mediated inhibition by itself binding to and masking the DNA, as well as by stimulating polymerization directly. The results suggest that in vivo, SopB smothers DNA by spreading from sopC, allowing SopA-ATP polymerization which initiates plasmid displacement. We propose that SopB and nucleoid DNA regulate SopA polymerization and hence partition.
在细菌中，质粒和许多染色体的有丝分裂稳定性取决于复制子特异性系统，该系统由一个着丝粒、一个着丝粒结合蛋白和一个ATP酶组成。ATP酶的动态自组装似乎能够使复制子拷贝主动分配到细胞的两个半区，但对于大多数ATP酶（沃克盒型）来说，其机制尚不清楚。宿主细胞如何促进分配也不清楚。我们研究了非序列特异性DNA对质粒F的SopA分配ATP酶体外自组装的影响。只要有ATP存在，SopA就会发生聚合。DNA抑制这种聚合，并导致预先形成的聚合物分解。着丝粒结合蛋白SopB通过自身结合并掩盖DNA以及直接刺激聚合来抵消DNA介导的抑制作用。结果表明，在体内，SopB从sopC扩散开来，覆盖DNA，从而允许SopA-ATP聚合，启动质粒移位。我们提出，SopB和类核DNA调节SopA聚合，进而调节分配。
