Bramkamp Marc, Emmins Robyn, Weston Louise, Donovan Catriona, Daniel Richard A, Errington Jeff
Institute for Biochemistry, University of Cologne, Zülpicher Str. 47, D-50674, Germany.
Mol Microbiol. 2008 Dec;70(6):1556-69. doi: 10.1111/j.1365-2958.2008.06501.x. Epub 2008 Oct 23.
Cell division in bacteria is governed by a complex cytokinetic machinery in which the key player is a tubulin homologue, FtsZ. Most rod-shaped bacteria divide precisely at mid-cell between segregated sister chromosomes. Selection of the correct site for cell division is thought to be determined by two negative regulatory systems: the nucleoid occlusion system, which prevents division in the vicinity of the chromosomes, and the Min system, which prevents inappropriate division at the cell poles. In Bacillus subtilis recruitment of the division inhibitor MinCD to cell poles depends on DivIVA, and these proteins were thought to be sufficient for Min function. We have now identified a novel component of the division-site selection system, MinJ, which bridges DivIVA and MinD. minJ mutants are impaired in division because MinCD activity is no longer restricted to cell poles. Although MinCD was thought to act specifically on FtsZ assembly, analysis of minJ and divIVA mutants showed that their block in division occurs downstream of FtsZ. The results support a model in which the main function of the Min system lies in allowing only a single round of division per cell cycle, and that MinCD acts at multiple levels to prevent inappropriate division.
细菌中的细胞分裂受一种复杂的细胞动力机制调控，其中关键角色是一种微管蛋白同源物FtsZ。大多数杆状细菌精确地在已分离的姐妹染色体之间的细胞中部进行分裂。细胞分裂正确位点的选择被认为由两个负调控系统决定：核仁封闭系统，它可防止在染色体附近进行分裂；以及Min系统，它可防止在细胞两极发生不适当的分裂。在枯草芽孢杆菌中，分裂抑制剂MinCD定位于细胞两极依赖于DivIVA，并且这些蛋白质被认为足以发挥Min系统的功能。我们现在鉴定出了分裂位点选择系统的一个新组分MinJ，它连接DivIVA和MinD。minJ突变体在分裂方面存在缺陷，因为MinCD的活性不再局限于细胞两极。尽管MinCD被认为特异性作用于FtsZ组装，但对minJ和divIVA突变体的分析表明，它们在分裂方面的阻滞发生在FtsZ下游。这些结果支持了这样一种模型，即Min系统的主要功能在于每个细胞周期仅允许一轮分裂，并且MinCD在多个层面发挥作用以防止不适当的分裂。
