CbtA toxin of Escherichia coli inhibits cell division and cell elongation via direct and independent interactions with FtsZ and MreB.
CbtA toxin of Escherichia coli inhibits cell division and cell elongation via direct and independent interactions with FtsZ and MreB.
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DOI：
10.1371/journal.pgen.1007007
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发表时间：
2017-09
期刊：
影响因子：
4.5
通讯作者：
Hochschild A
中科院分区：
文献类型：
--
作者：
Heller DM;Tavag M;Hochschild A
在细菌质粒、质粒和染色体中发现的毒素-抗毒素模块的毒素组分通常靶向单个大分子以干扰基本的细胞过程。一个明显的例外是E. coliCbtA/CbeA毒素-抗毒素模块，能抑制细胞分裂和细胞伸长。一个只有124个氨基酸的小蛋白质，CbtA，以前提出与FtsZ，微管蛋白同源物，是细胞分裂所必需的，和MreB，肌动蛋白同源物，是细胞伸长所必需的。然而，CbtA的毒性作用是否是由于与这些预测的靶点直接相互作用而引起的尚不清楚。在这里，我们从遗传学上分离了CbtA对细胞伸长和细胞分裂的影响，表明CbtA直接且独立地与FtsZ和MreB相互作用。使用互补的遗传方法，我们确定FtsZ和MreB的功能相关的目标表面，揭示在这两种情况下，CbtA结合到参与基本的细胞骨架丝结构的表面。我们进一步表明，每个相互作用独立地有助于CbtA介导的毒性和破坏这两个相互作用是必要的，以减轻所观察到的毒性。虽然已知其他几种蛋白质调节剂靶向FtsZ，但我们确定的CbtA相互作用表面代表了一种新的抑制性靶点。我们的研究结果建立CbtA作为一个双重功能的毒素，抑制细胞分裂和细胞伸长通过直接和独立的相互作用与FtsZ和MreB。细菌编码的毒素-抗毒素系统由与中和抗毒素共同产生的小毒素蛋白组成，是鉴定新型抗生素靶标的潜在途径。这些毒素通常靶向基本的细胞过程，当不受抗毒素抑制时导致生长停滞或细胞死亡。本实验主要研究大肠杆菌的CbtA毒素。大肠杆菌，已知其抑制细菌细胞分裂和细菌细胞伸长（杆状细菌在细胞分裂之前生长的过程）。我们报告说，CbtA对细胞分裂和细胞伸长的影响是遗传上可分离的，它们是由于直接和独立的相互作用，其目标FtsZ和MreB，基本的细胞骨架蛋白，直接细胞分裂和细胞伸长，分别。我们的遗传分析定义了FtsZ和MreB上功能相关的靶表面;在FtsZ的情况下，该表面代表了一种新的抑制性靶点。作为一种独立靶向两种基本细胞骨架元件的双功能毒素，CbtA可以指导双功能抗生素的设计，其独立靶向一种以上基本细胞过程的能力可能会阻碍耐药性的发展，这是一个日益严重的公共卫生威胁。
The toxin components of toxin-antitoxin modules, found in bacterial plasmids, phages, and chromosomes, typically target a single macromolecule to interfere with an essential cellular process. An apparent exception is the chromosomally encoded toxin component of the E. coli CbtA/CbeA toxin-antitoxin module, which can inhibit both cell division and cell elongation. A small protein of only 124 amino acids, CbtA, was previously proposed to interact with both FtsZ, a tubulin homolog that is essential for cell division, and MreB, an actin homolog that is essential for cell elongation. However, whether or not the toxic effects of CbtA are due to direct interactions with these predicted targets is not known. Here, we genetically separate the effects of CbtA on cell elongation and cell division, showing that CbtA interacts directly and independently with FtsZ and MreB. Using complementary genetic approaches, we identify the functionally relevant target surfaces on FtsZ and MreB, revealing that in both cases, CbtA binds to surfaces involved in essential cytoskeletal filament architecture. We show further that each interaction contributes independently to CbtA-mediated toxicity and that disruption of both interactions is required to alleviate the observed toxicity. Although several other protein modulators are known to target FtsZ, the CbtA-interacting surface we identify represents a novel inhibitory target. Our findings establish CbtA as a dual function toxin that inhibits both cell division and cell elongation via direct and independent interactions with FtsZ and MreB. Bacterially encoded toxin-antitoxin systems, which consist of a small toxin protein that is co-produced with a neutralizing antitoxin, are a potential avenue for the identification of novel antibiotic targets. These toxins typically target essential cellular processes, causing growth arrest or cell death when unchecked by the antitoxin. Our study is focused on the CbtA toxin of E. coli, which was known to inhibit both bacterial cell division and also bacterial cell elongation (the process by which rod-shaped bacteria grow prior to cell division). We report that the effects of CbtA on cell division and cell elongation are genetically separable, and that they are due to direct and independent interactions with its targets FtsZ and MreB, essential cytoskeletal proteins that direct cell division and cell elongation, respectively. Our genetic analysis defines the functionally relevant target surfaces on FtsZ and MreB; in the case of FtsZ this surface represents a novel inhibitory target. As a dual-function toxin that independently targets two essential cytoskeletal elements, CbtA could guide the design of dual-function antibiotics whose ability to independently target more than one essential cellular process might impede the development of drug resistance, which is a growing public health threat.
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