FtsZ directs a second mode of peptidoglycan synthesis in Escherichia coli
FtsZ directs a second mode of peptidoglycan synthesis in Escherichia coli
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DOI：
10.1128/jb.00455-07
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发表时间：
2007-08-01
影响因子：
3.2
通讯作者：
Young, Kevin D.
中科院分区：
文献类型：
--
作者：
Varma, Archana;de Pedro, Miguel A.;Young, Kevin D.
当FtsZ蛋白被抑制时，大肠杆菌的某些青霉素结合蛋白突变体生长具有类似于大肠杆菌的形态，这表明FtsZ可能支配细胞壁生长的方面，而不是与分隔严格相关的方面。在研究螺旋细胞形成的机制时，我们发现了使FtsZ的第二种功能可视化的条件。通常，抑制细胞骨架蛋白MreB迫使E.大肠杆菌细胞生长为平滑的扩大的球体，其中两极消失，产生球形或柠檬形的形式。然而，当FtsZ和MreB在缺乏PBP 5和PBP 7的菌株中同时被抑制时，所产生的细胞向外膨胀，但在代表原始极点的位点处保留明显的杆状延伸。这种视觉表型是由球囊生长的生物化学决定的。鼠肽通常被均匀地插入到侧细胞壁中，但是当FtsZ聚合被抑制时，新材料的掺入主要发生在细胞的中心区域，并且在邻接极的侧壁的那些部分中显著较低。因此，减少前体掺入到侧壁附近的两极解释了为什么这些地区保留其棒状形态，而其余的细胞球形生长。此外，抑制FtsZ增加了约三分之一的球囊中的五肽的量。最后，MreB蛋白指导新的肽聚糖螺旋或对角掺入到壁中，但掺入的位置取决于FtsZ是否有活性。总之，结果表明，除了成核细胞分隔在E。在大肠杆菌中，FtsZ可以引导新的肽聚糖插入到侧壁的部分中。
Certain penicillin binding protein mutants of Escherichia coli grow with spirillum-like morphologies when the FtsZ protein is inhibited, suggesting that FtsZ might govern aspects of cell wall growth other than those strictly associated with septation. While investigating the mechanism of spiral cell formation, we discovered conditions for visualizing this second function of FtsZ. Normally, inhibiting the cytoskeleton protein MreB forces E. coli cells to grow as smoothly enlarging spheres from which the poles disappear, yielding coccoid or lemon-shaped forms. However, when FtsZ and MreB were inhibited simultaneously in a strain lacking PBP 5 and PBP 7, the resulting cells ballooned outward but retained conspicuous rod-shaped extensions at sites representing the original poles. This visual phenotype was paralleled by the biochemistry of sacculus growth. Muropeptides are usually inserted homogeneously into the lateral cell walls, but when FtsZ polymerization was inhibited, the incorporation of new material occurred mainly in the central regions of cells and was significantly lower in those portions of side walls abutting a pole. Thus, reduced precursor incorporation into side walls near the poles explained why these regions retained their rod-like morphology while the rest of the cell grew spherically. Also, inhibiting FtsZ increased the amount of pentapeptides in sacculi by about one-third. Finally, the MreB protein directed the helical or diagonal incorporation of new peptidoglycan into the wall, but the location of that incorporation depended on whether FtsZ was active. In sum, the results indicate that in addition to nucleating cell septation in E. coli, FtsZ can direct the insertion of new peptidoglycan into portions of the lateral wall.