MurJ and a novel lipid II flippase are required for cell wall biogenesis in Bacillus subtilis
MurJ and a novel lipid II flippase are required for cell wall biogenesis in Bacillus subtilis
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DOI：
10.1073/pnas.1504967112
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发表时间：
2015-05-19
影响因子：
11.1
通讯作者：
Rudner, David Z.
中科院分区：
文献类型：
--
作者：
Meeske, Alexander J.;Sham, Lok-To;Rudner, David Z.
细菌表面多糖是由细胞质膜内表面的脂联前体合成的，然后通过双层转运进行包膜组装。大肠杆菌细胞壁前体脂质II的转运需要广泛保守和必需的多药/寡糖基脂质/多糖（MOP）出口超家族成员MurJ。在这里，我们发现枯草芽孢杆菌细胞缺乏所有10个MOP超家族成员，只有轻微的形态学缺陷，证明存在另一种脂质II翻转酶。为了确定这一因素，我们使用转座子测序筛选MOP家族成员的合成致死伴侣。我们发现了一个未表征的基因amj（替代MurJ； ydaH）和枯草芽孢杆菌MurJ (MurJ (Bs)；原ytgP)是合成致命的一对。Amj和MurJ(b)缺陷的细胞表现为细胞形状缺陷和裂解。此外，在没有大肠杆菌MurJ的情况下，Amj或MurJ（Bs）在大肠杆菌中的表达支持脂质II翻转和生存能力。Amj存在于革兰氏阴性和革兰氏阳性细菌的一个亚群中，是一个新的翻转酶家族的创始成员。最后，我们发现Amj在细胞包膜应激反应转录因子sigma(M)的控制下表达，缺乏MurJ（Bs）的细胞会增加Amj的转录。这些发现提出了一种可能性，即典型MurJ翻转酶的拮抗剂会触发一种可抵抗抑制的替代转座酶的表达。
Bacterial surface polysaccharides are synthesized from lipid-linked precursors at the inner surface of the cytoplasmic membrane before being translocated across the bilayer for envelope assembly. Transport of the cell wall precursor lipid II in Escherichia coli requires the broadly conserved and essential multidrug/oligosaccharidyl- lipid/polysaccharide (MOP) exporter superfamily member MurJ. Here, we show that Bacillus subtilis cells lacking all 10 MOP superfamily members are viable with only minor morphological defects, arguing for the existence of an alternate lipid II flippase. To identify this factor, we screened for synthetic lethal partners of MOP family members using transposon sequencing. We discovered that an uncharacterized gene amj (alternate to MurJ; ydaH) and B. subtilis MurJ (murJ(Bs); formerly ytgP) are a synthetic lethal pair. Cells defective for both Amj and MurJ(Bs) exhibit cell shape defects and lyse. Furthermore, expression of Amj or MurJ(Bs) in E. coli supports lipid II flipping and viability in the absence of E. coli MurJ. Amj is present in a subset of gram-negative and gram-positive bacteria and is the founding member of a novel family of flippases. Finally, we show that Amj is expressed under the control of the cell envelope stress-response transcription factor sigma(M) and cells lacking MurJ(Bs) increase amj transcription. These findings raise the possibility that antagonists of the canonical MurJ flippase trigger expression of an alternate translocase that can resist inhibition.