Inactivation of FtsI inhibits constriction of the FtsZ cytokinetic ring and delays the assembly of FtsZ rings at potential division sites
Inactivation of FtsI inhibits constriction of the FtsZ cytokinetic ring and delays the assembly of FtsZ rings at potential division sites
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DOI：
10.1073/pnas.94.2.559
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发表时间：
1997-01-21
影响因子：
11.1
通讯作者：
Beckwith, J
中科院分区：
文献类型：
--
作者：
Pogliano, J;Pogliano, K;Beckwith, J
细胞分裂中的一个普遍保守的事件是在未来的分裂位点形成细胞动力学环，在大肠杆菌中，该环由必需的细胞分裂蛋白FtsZ形成。我们已经使用免疫荧光显微镜显示，FtsZ组装在分裂周期的早期，表明FtsZ环的收缩调节和支持的观点，FtsZ作为细菌的细胞骨架。FtsZ环的组装在非允许温度下生长的ftsI温度敏感突变体中受到异质性影响，一些细丝在FtsZ组装中显示出明显的缺陷，而其他细丝显示很少或没有缺陷。通过使用低浓度的β-内酰胺类头孢氨苄和哌拉西林，以特异性地抑制FtsI（PBP 3），一种在分裂隔膜合成肽聚糖的酶，我们表明，FtsZ环收缩需要FtsI的转肽酶活性，未收缩的FtsZ环被稳定地捕获在细胞的中点几代FtsI失活后，而部分收缩的FtsZ环被有效地捕获。此外，FtsZ环能够在头孢氨苄存在下在新生细胞中组装，这表明新生细胞含有FtsZ可以组装的位点然而，除了第一轮FtsZ环组装外，在头孢氨苄存在下很少有额外的FtsZ环组装，甚至在生长几代之后，对这些结果的一种解释是，FtsI的转肽酶活性对于新生分裂位点的组装以及因此对于FtsZ环的未来组装是直接或间接需要的。
A universally conserved event in cell division is the formation of a cytokinetic ring at the future site of division, In the bacterium Escherichia coli, this ring is formed by the essential cell division protein FtsZ. We have used immunofluorescence microscopy to show that FtsZ assembles early in the division cycle, suggesting that constriction of the FtsZ ring is regulated and supporting the view that FtsZ serves as a bacterial cytoskeleton. Assembly of FtsZ rings was heterogeneously affected in an ftsI temperature-sensitive mutant grown at the nonpermissive temperature, some filaments displaying a striking defect in FtsZ assembly and others displaying little or no defect. By using low concentrations of the beta-lactams cephalexin and piperacillin to specifically inhibit FtsI (PBP3), an enzyme that synthesizes peptidoglycan at the division septum, we show that FtsZ ring constriction requires the transpeptidase activity of FtsI, Unconstricted FtsZ rings are stably trapped at the midpoint of the cell for several generations after inactivation of FtsI, whereas partially constricted FtsZ rings are less effectively trapped. In addition, FtsZ rings are able to assemble in newborn cells in the presence of cephalexin, suggesting that newborn cells contain a site at which FtsZ can assemble (the nascent division site) and that the transpeptidase activity of FtsI is not required for assembly of FtsZ at these sites, However, aside from this first round of FtsZ ring assembly, very few additional FtsZ rings assemble in the presence of cephalexin, even after several generations of growth, One interpretation of these results is that the transpeptidase activity of FtsI is required, directly or indirectly, for the assembly of nascent division sites and thereby for future assembly of FtsZ rings.