Shifts from glucose to certain secondary carbon-sources result in activation of the extracytoplasmic function sigma factor sigmaE in Salmonella enterica serovar Typhimurium.
Shifts from glucose to certain secondary carbon-sources result in activation of the extracytoplasmic function sigma factor sigmaE in Salmonella enterica serovar Typhimurium.
复制标题
从葡萄糖到某些次级碳源的转变导致鼠伤寒沙门氏菌中胞质外功能 sigma 因子 sigmaE 的激活。
DOI：
10.1099/mic.0.27649-0
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
Spector,MichaelP
中科院分区：
文献类型：
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作者：
Kenyon,WilliamJ;Thomas,SheenaM;Johnson,Erin;Pallen,MarkJ;Spector,MichaelP
鼠伤寒沙门氏菌（Salmonella entericaserovar Typhimurium）鼠伤寒沙门氏菌（Typhimurium）由于对必需营养素（例如碳/能源（C源））的饥饿而引起饥饿应激反应（SSR）。作为SSR的一部分，替代σ因子σ E被激活并被诱导。作者怀疑这种激活部分是由S的变化触发的。在从生长到碳/能量饥饿（C-饥饿）的适应过程中发生的鼠伤寒沙门氏菌细胞被膜，导致对σ E调节因子的需求增加，这些因子参与了新合成蛋白质的正确折叠和组装，这些蛋白质将进入该细胞质外区室。这导致了一种假设，即在C源移位期间可能出现σEactivation信号，该C源移位导致定位于细胞外质区室（即细胞的外膜或周质）的蛋白质的诱导。为了测试该假设，使培养物在含有足够葡萄糖以达到中期指数期的基本培养基中生长，加上非限制量的次要“不太优选”但可利用的碳/能源。然后使用携带rpoEP 1-和rpoEP 2-lacZ转录融合体的质粒监测σ E活性，这两种质粒分别表现出σ E非依赖性和σ E依赖性lacZ表达。次级碳源麦芽糖、琥珀酸盐和柠檬酸盐具有参与其利用的细胞质外组分（例如LamB），导致可辨别的二次生长滞后期和σ E活性的持续增加。从葡萄糖到其他可利用的磷酸转移酶（PTS）和非PTS C-源（如海藻糖、甘露糖、甘露醇、果糖、甘油、d-半乳糖或l-阿拉伯糖）的生长过渡不会引起明显的二次生长滞后期或σ E活性的持续增加。有趣的是，从葡萄糖到蜜二糖的转变（不使用位于细胞质外的蛋白质进行摄取）确实引起了可观察到的二次生长滞后期，但并未导致σ E活性的持续增加。此外，在不存在葡萄糖至麦芽糖转变或C饥饿的情况下，来自阿拉伯糖诱导型启动子的LamB的过表达导致σ E活性的显著增加。此外，缺乏LamB麦芽糖孔蛋白的ΔlamB：：Ω-Kmr突变体在葡萄糖至麦芽糖转变期间观察到的持续σ E活性显示出约两倍的降低，再次支持该假设。 有趣的是，LamB蛋白缺乏OmpC样肽的典型Y-X-F末端三肽，其激活DegS蛋白酶活性，导致σ E激活。然而，它确实具有末端五肽（Q-M-E-I-W-W），其可以作为推定的II类PDZ结合位点的配体起作用。因此，作者提出S.鼠伤寒沙门氏菌不仅在有害的环境条件下被诱导，而且在细胞适应新的生长条件中发挥作用，这些条件需要细胞的胞质外区室发生变化，这可能涉及独立于DegS的替代信号识别和激活途径。
Salmonella entericaserovar Typhimurium (S. Typhimurium) elicits the starvation-stress response (SSR) due to starvation for an essential nutrient, e.g. a carbon/energy source (C-source). As part of the SSR, the alternative sigma factorσEis activated and induced. The authors suspect that this activation is, in part, triggered by changes in theS. Typhimurium cell envelope occurring during the adaptation from growth to carbon/energy starvation (C-starvation), and resulting in an increased need forσE-regulated factors involved in the proper folding and assembly of newly synthesized proteins destined for this extracytoplasmic compartment. This led to the hypothesis that aσEactivation signal might arise during C-source shifts that cause the induction of proteins localized to the extracytoplasmic compartment, i.e. the outer membrane or periplasm, of the cell. To test this hypothesis, cultures were grown in minimal medium containing enough glucose to reach mid-exponential-phase, plus a non-limiting amount of a secondary ‘less-preferred’ but utilizable carbon/energy source. TheσEactivity was then monitored using plasmids carryingrpoEP1– andrpoEP2–lacZtranscriptional fusions, which exhibitσE-independent and -dependentlacZexpression, respectively. The secondary C-sources maltose, succinate and citrate, which have extracytoplasmic components involved in their utilization (e.g. LamB), resulted in a discernible diauxic lag period and a sustained increase inσEactivity. Growth transition from glucose to other utilizable phosphotransferase (PTS) and non-PTS C-sources, such as trehalose, mannose, mannitol, fructose, glycerol,d-galactose orl-arabinose, did not cause a discernible diauxic lag period or a sustained increase inσEactivity. Interestingly, a shift from glucose to melibiose, which does not use an extracytoplasmic-localized protein for uptake, did cause an observable diauxic lag period but did not result in a sustained increase inσEactivity. In addition, overexpression of LamB from an arabinose-inducible promoter leads to a significant increase inσEactivity in the absence of a glucose to maltose shift or C-starvation. Furthermore, a ΔlamB: : Ω-Kmrmutant, lacking the LamB maltoporin, exhibited an approximately twofold reduction in the sustainedσEactivity observed during a glucose to maltose shift, again supporting the hypothesis. Interestingly, the LamB protein lacks the typical Y-X-F terminal tripeptide of the OmpC-like peptides that activate DegS protease activity leading toσEactivation. It does, however, possess a terminal pentapeptide (Q-M-E-I-W-W) that may function as a ligand for a putative class II PDZ-binding site. The authors therefore propose that theσEregulon ofS. Typhimurium not only is induced in response to deleterious environmental conditions, but also plays a role in the adaptation of cells to new growth conditions that necessitate changes in the extracytoplasmic compartment of the cell, which may involve alternative signal recognition and activation pathways that are independent of DegS.