Two independent spiral structures control cell shape in Caulobacter
Two independent spiral structures control cell shape in Caulobacter
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DOI：
10.1073/pnas.0507708102
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发表时间：
2005-12-20
影响因子：
11.1
通讯作者：
Gitai, Z
中科院分区：
文献类型：
--
作者：
Dye, NA;Pincus, Z;Gitai, Z
肌动蛋白同源物MreB有助于细菌细胞的形状。在这里，我们探讨了在柄杆菌共表达的MreC蛋白的作用，并表明它形成了一个周质螺旋，是与细胞质MreB螺旋的相位。mreB和mreC都是必不可少的，任何一种蛋白质的缺失都会导致类似的细胞形状缺陷。MreB在MreC缺失的细胞中形成动态螺旋，并且MreC在MreB抑制剂A22存在下螺旋定位，这表明每种蛋白质可以独立于另一种蛋白质形成螺旋。我们发现，肽聚糖转肽酶Pbp 2也形成了一个螺旋模式，部分共定位与MreC，但不是MreB。干扰MreB（A22）或MreC（耗尽）导致GFP-Pbp 2错误定位到分裂平面，表明每一个都是必要的，但不足以产生螺旋Pbp 2模式。我们表明，这是分裂过程中，提请Pbp 2中细胞的MreB的调节的情况下，因为细胞耗尽的微管蛋白同系物FtsZ保持螺旋Pbp 2的本地化A22的存在下。通过开发和采用以前未表征的计算方法定量形状方差，我们发现，FtsZ耗尽也可以部分挽救A22诱导的形状变形。我们的结论是，MreB和MreC形成空间上不同的和独立本地化的螺旋，并提出MreB抑制分裂平面本地化的Pbp 2，而MreC促进纵向本地化的Pbp 2，这两个机制一起确保螺旋本地化的Pbp 2，从而，维护适当的细胞形态柄杆菌。
The actin homolog MreB contributes to bacterial cell shape. Here, we explore the role of the coexpressed MreC protein in Caulobacter and show that it forms a periplasmic spiral that is out of phase with the cytoplasmic MreB spiral. Both mreB and mreC are essential, and depletion of either protein results in a similar cell shape defect. MreB forms dynamic spirals in MreC-depleted cells, and MreC localizes helically in the presence of the MreB-inhibitor A22, indicating that each protein can form a spiral independently of the other. We show that the peptidoglycan transpeptidase Pbp2 also forms a helical pattern that partially colocalizes with MreC but not MreB. Perturbing either MreB (with A22) or MreC (with depletion) causes GFP-Pbp2 to mislocalize to the division plane, indicating that each is necessary but not sufficient to generate a helical Pbp2 pattern. We show that it is the division process that draws Pbp2 to midcell in the absence of MreB's regulation, because cells depleted of the tubulin homolog FtsZ maintain a helical Pbp2 localization in the presence of A22. By developing and employing a previously uncharacterized computational method for quantitating shape variance, we find that a FtsZ depletion can also partially rescue the A22-induced shape deformation. We conclude that MreB and MreC form spatially distinct and independently localized spirals and propose that MreB inhibits division plane localization of Pbp2, whereas MreC promotes lengthwise localization of Pbp2; together these two mechanism ensure a helical localization of Pbp2 and, thereby, the maintenance of proper cell morphology in Caulobacter.