Ebersbach Gitte, Galli Elisa, Møller-Jensen Jakob, Löwe Jan, Gerdes Kenn
Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
Mol Microbiol. 2008 May;68(3):720-35. doi: 10.1111/j.1365-2958.2008.06190.x.
Formation of the Z ring is the first known event in bacterial cell division. However, it is not yet known how the assembly and contraction of the Z ring are regulated. Here, we identify a novel cell division factor ZapB in Escherichia coli that simultaneously stimulates Z ring assembly and cell division. Deletion of zapB resulted in delayed cell division and the formation of ectopic Z rings and spirals, whereas overexpression of ZapB resulted in nucleoid condensation and aberrant cell divisions. Localization of ZapB to the divisome depended on FtsZ but not FtsA, ZipA or FtsI, and ZapB interacted with FtsZ in a bacterial two-hybrid analysis. The simultaneous inactivation of FtsA and ZipA prevented Z ring assembly and ZapB localization. Time lapse microscopy showed that ZapB-GFP is present at mid-cell in a pattern very similar to that of FtsZ. Cells carrying a zapB deletion and the ftsZ84(ts) allele exhibited a synthetic sick phenotype and aberrant cell divisions. The crystal structure showed that ZapB exists as a dimer that is 100% coiled-coil. In vitro, ZapB self-assembled into long filaments and bundles. These results raise the possibility that ZapB stimulates Z ring formation directly via its capacity to self-assemble into larger structures.
Z环的形成是细菌细胞分裂中已知的首个事件。然而，Z环的组装和收缩是如何被调控的目前仍不清楚。在此，我们在大肠杆菌中鉴定出一种新型细胞分裂因子ZapB，它能同时刺激Z环组装和细胞分裂。缺失zapB会导致细胞分裂延迟以及异位Z环和螺旋的形成，而ZapB的过表达则会导致类核凝聚和异常细胞分裂。ZapB在分裂体上的定位依赖于FtsZ，但不依赖于FtsA、ZipA或FtsI，并且在细菌双杂交分析中ZapB与FtsZ相互作用。FtsA和ZipA的同时失活会阻止Z环组装和ZapB定位。延时显微镜观察显示，ZapB-GFP以与FtsZ非常相似的模式出现在细胞中部。携带zapB缺失和ftsZ84(ts)等位基因的细胞表现出合成病表型和异常细胞分裂。晶体结构显示ZapB以100%卷曲螺旋的二聚体形式存在。在体外，ZapB自组装成长丝和束。这些结果增加了ZapB通过其自组装成更大结构的能力直接刺激Z环形成的可能性。
