NlpD links cell wall remodeling and outer membrane invagination during cytokinesis in Escherichia coli
NlpD links cell wall remodeling and outer membrane invagination during cytokinesis in Escherichia coli
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DOI：
10.1371/journal.pgen.1006888
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发表时间：
2017-07-01
期刊：
影响因子：
4.5
通讯作者：
Bernhardt, Thomas G.
中科院分区：
文献类型：
--
作者：
Tsang, Mary-Jane;Yakhnina, Anastasiya A.;Bernhardt, Thomas G.
革兰氏阴性菌的细胞质分裂需要所有三个细胞包膜层的收缩：内膜（IM），肽聚糖（PG）细胞壁和外膜（OM）。为了避免细胞完整性的潜在致命破坏，这种细胞表面的戏剧性重塑需要细胞动力学环的不同包膜重塑活动的紧密协调。然而，负责这种协调的机制仍然不明确。包膜重塑过程中为数不多的特征调控点之一是被称为酰胺酶的细胞壁水解酶的激活。这些酶分裂由发育中的子细胞共享的细胞壁物质，以促进它们最终的分离。在大肠杆菌中，酰胺酶活性需要两种部分冗余的激活剂之一的刺激：EnvC（与IM相关）和NlpD（锚定在OM中的脂蛋白）。在这里，我们研究了NlpD对酰胺酶激活的调节。结构-功能分析表明，NlpD的OM定位对调节其酰胺酶激活活性至关重要。为了确定NlpD细胞分离途径中涉及的其他因素，我们还开发了一种基于流式细胞术的富集程序的遗传筛选。这种策略使我们能够分离出在冗余EnvC通路失活时形成长链未分离细胞的突变体。结果显示，toll - pal系统和YraP参与了NlpD的激活。托pal系统被认为促进OM内陷在分割部位。YraP是一种功能未知的保守蛋白，我们已经确定它是细胞动力学环的一个新的om定位成分。总的来说，我们的研究结果支持一个模型，即分裂部位的OM和PG重塑事件部分通过NlpD激活与OM内陷的耦合而协调。
Cytokinesis in gram-negative bacteria requires the constriction of all three cell envelope layers: the inner membrane (IM), the peptidoglycan (PG) cell wall and the outer membrane (OM). In order to avoid potentially lethal breaches in cell integrity, this dramatic reshaping of the cell surface requires tight coordination of the different envelope remodeling activities of the cytokinetic ring. However, the mechanisms responsible for this coordination remain poorly defined. One of the few characterized regulatory points in the envelope remodeling process is the activation of cell wall hydrolytic enzymes called amidases. These enzymes split cell wall material shared by developing daughter cells to facilitate their eventual separation. In Escherichia coli, amidase activity requires stimulation by one of two partially redundant activators: EnvC, which is associated with the IM, and NlpD, a lipoprotein anchored in the OM. Here, we investigate the regulation of amidase activation by NlpD. Structure-function analysis revealed that the OM localization of NlpD is critical for regulating its amidase activation activity. To identify additional factors involved in the NlpD cell separation pathway, we also developed a genetic screen using a flow cytometry-based enrichment procedure. This strategy allowed us to isolate mutants that form long chains of unseparated cells specifically when the redundant EnvC pathway is inactivated. The screen implicated the Tol-Pal system and YraP in NlpD activation. The Tol-Pal system is thought to promote OM invagination at the division site. YraP is a conserved protein of unknown function that we have identified as a new OM-localized component of the cytokinetic ring. Overall, our results support a model in which OM and PG remodeling events at the division site are coordinated in part through the coupling of NlpD activation with OM invagination.