Molecular Basis of Lipopolysaccharide Heterogeneity in Escherichia coli
Molecular Basis of Lipopolysaccharide Heterogeneity in Escherichia coli
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大肠杆菌脂多糖异质性的分子基础
DOI：
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发表时间：
2011
影响因子：
4.8
通讯作者：
S. Raina
中科院分区：
文献类型：
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作者：
G. Klein;B. Lindner;H. Brade;S. Raina
背景：LPS对生存能力至关重要，尽管它是高度异质性的。结果：不同糖型的合成受KdoIII转移酶WaaZ和糖基转移酶WaaR的差异表达调控。rpoe转录的rybB sRNA抑制WaaR的合成，在rpoe诱导条件下，KdoIII的结合需要ppGpp。结论：RpoE诱导导致外核截断，鼠李糖增加KdoIII。意义：LPS改变对外膜功能至关重要。waa位点非极性突变或同源基因过表达的等基因大肠杆菌的脂多糖（LPS）质谱分析表明，waaZ和waaS分别是与Kdo双糖和鼠李糖相连的第三个3-脱氧-α-d-甘露糖-oct-2-乌糖酸（Kdo）结合所需的结构基因。鼠李糖的掺入需要先顺序掺入Kdo三糖。来自ΔwaaO的脂质a锚定的最小体内核心结构Kdo2Hep2Hex2P1（缺乏α-1,3-葡萄糖基转移酶）可以结合Kdo3Rha，而不过度表达waaZ和waaS基因。对LPS异质性的检验表明，RpoE σ因子、双组分系统（BasS/R和PhoB/R）和ppGpp控制重叠。rpoe特异性抗σ因子rseA的缺失导致与Kdo双糖连接的第三个Kdo的糖型几乎完全结合。这伴随着鼠李糖的合并，连接到末端的第三个Kdo或第二个Kdo，取决于磷酸乙醇胺在第二个Kdo上的存在或不存在，外核被截断。ΔrseA中的这种截断归因于WaaR糖基转移酶水平的降低，在引入rybB sRNA缺失后，WaaR糖基转移酶恢复到野生型水平，包括整体LPS组成。因此，ΔwaaR主要含有Kdo3的LPS，不需要脂质A修饰。与Kdo3和4-氨基-4-脱氧-l-阿拉伯糖在脂质a中的积累需要ppGpp，在Δ中被消除（ppGpp0 rseA）。此外，合成四酰化脂质A的Δ（waaZ lpxLMP）在21-23°C时表现出合成致死率，这表明第三个Kdo的掺入具有重要意义。
Background: LPS is essential for viability, although it is highly heterogeneous. Results: Synthesis of different glycoforms is regulated by differential expression of WaaZ (KdoIII transferase) and WaaR (glycosyltransferase). RpoE-transcribed rybB sRNA represses WaaR synthesis, and ppGpp is required for KdoIII incorporation in RpoE-inducing conditions. Conclusion: RpoE induction causes truncation of outer core and rhamnose addition to KdoIII. Significance: LPS alterations are crucial for outer membrane function. Mass spectrometric analyses of lipopolysaccharide (LPS) from isogenic Escherichia coli strains with nonpolar mutations in the waa locus or overexpression of their cognate genes revealed that waaZ and waaS are the structural genes required for the incorporation of the third 3-deoxy-α-d-manno-oct-2-ulosonic acid (Kdo) linked to Kdo disaccharide and rhamnose, respectively. The incorporation of rhamnose requires prior sequential incorporation of the Kdo trisaccharide. The minimal in vivo lipid A-anchored core structure Kdo2Hep2Hex2P1 in the LPS from ΔwaaO (lacking α-1,3-glucosyltransferase) could incorporate Kdo3Rha, without the overexpression of the waaZ and waaS genes. Examination of LPS heterogeneity revealed overlapping control by RpoE σ factor, two-component systems (BasS/R and PhoB/R), and ppGpp. Deletion of RpoE-specific anti-σ factor rseA led to near-exclusive incorporation of glycoforms with the third Kdo linked to Kdo disaccharide. This was accompanied by concomitant incorporation of rhamnose, linked to either the terminal third Kdo or to the second Kdo, depending upon the presence or absence of phosphoethanolamine on the second Kdo with truncation of the outer core. This truncation in ΔrseA was ascribed to decreased levels of WaaR glycosyltransferase, which was restored to wild-type levels, including overall LPS composition, upon the introduction of rybB sRNA deletion. Thus, ΔwaaR contained LPS primarily with Kdo3 without any requirement for lipid A modifications. Accumulation of a glycoform with Kdo3 and 4-amino-4-deoxy-l-arabinose in lipid A in ΔrseA required ppGpp, being abolished in a Δ(ppGpp0 rseA). Furthermore, Δ(waaZ lpxLMP) synthesizing tetraacylated lipid A exhibited synthetic lethality at 21–23°C pointing to the significance of the incorporation of the third Kdo.
影响因子：
10.5
作者：
MECSAS, J;ROUVIERE, PE;GROSS, CA
通讯作者：
GROSS, CA
影响因子：
3.5
作者：
SIMONS, RW;HOUMAN, F;KLECKNER, N
通讯作者：
KLECKNER, N