Bernhardt Thomas G, de Boer Piet A J
Department of Molecular Biology and Microbiology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Mol Cell. 2005 May 27;18(5):555-64. doi: 10.1016/j.molcel.2005.04.012.
Cell division in Escherichia coli begins with assembly of the tubulin-like FtsZ protein into a ring structure just underneath the cell membrane. Spatial control over Z ring assembly is achieved by two partially redundant negative regulatory systems, the Min system and nucleoid occlusion (NO), which cooperate to position the division site at midcell. In contrast to the well-studied Min system, almost nothing is known about how Z ring assembly is blocked in the vicinity of nucleoids to effect NO. Reasoning that Min function might become essential in cells impaired for NO, we screened for mutations synthetically lethal with a defective Min system (slm mutants). By using this approach, we identified SlmA (Ttk) as the first NO factor in E. coli. Our combined genetic, cytological, and biochemical results suggest that SlmA is a DNA-associated division inhibitor that is directly involved in preventing Z ring assembly on portions of the membrane surrounding the nucleoid.
大肠杆菌中的细胞分裂始于微管蛋白样FtsZ蛋白在细胞膜正下方组装成环形结构。对Z环组装的空间控制是通过两个部分冗余的负调控系统实现的，即Min系统和类核阻隔（NO），它们共同作用将分裂位点定位在细胞中部。与研究充分的Min系统不同，对于Z环组装如何在类核附近被阻断以实现NO，几乎一无所知。基于Min功能在NO受损的细胞中可能变得至关重要的推断，我们筛选了与缺陷Min系统合成致死的突变（slm突变体）。通过这种方法，我们鉴定出SlmA（Ttk）是大肠杆菌中的首个NO因子。我们综合的遗传学、细胞学和生物化学结果表明，SlmA是一种与DNA相关的分裂抑制剂，直接参与阻止Z环在围绕类核的部分膜上组装。
