Studies of regulation of expression of the propionate (prpBCDE) operon provide insights into how Salmonella typhimurium LT2 integrates its 1,2-propanediol and propionate catabolic pathways.
Studies of regulation of expression of the propionate (prpBCDE) operon provide insights into how Salmonella typhimurium LT2 integrates its 1,2-propanediol and propionate catabolic pathways.
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对丙酸 (prpBCDE) 操纵子表达调节的研究为了解鼠伤寒沙门氏菌 LT2 如何整合其 1,2-丙二醇和丙酸分解代谢途径提供了见解。
DOI：
10.1128/jb.180.24.6511-6518.1998
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发表时间：
1998
影响因子：
3.2
通讯作者：
Escalante-Semerena,JC
中科院分区：
文献类型：
--
作者：
Tsang,AW;Horswill,AR;Escalante-Semerena,JC
鼠伤寒沙门氏菌LT 2的prpBCDE操纵子的表达需要（i）通过PrpE蛋白或细胞的乙酰辅酶A合成系统合成丙酰辅酶A（CoA），以及（ii）通过PrpC蛋白从丙酰辅酶A和草酰乙酸合成2-甲基柠檬酸盐。我们建议，无论是2-甲基柠檬酸盐或其衍生物的信号丙酸在环境中的存在。这种尚未鉴定的信号被认为是PrpR活性的辅助调节因子，PrpR是激活prpBCDE转录所需的σ-54转录激活因子家族的成员。CobB蛋白也是prpBCDE操纵子表达所必需的，但其作用尚不清楚。在1，2-丙二醇诱导丙二醇利用（pdu）操纵子后，cobB突变体中prpBCDE操纵子的表达恢复到野生型水平。这种作用不需要1，2-丙二醇的催化剂，表明Pdu蛋白，而不是1，2-丙二醇的分解代谢产物，是观察到的效果的原因。我们解释了这些冗余功能的代谢途径整合方面的存在。在以1，2-丙二醇作为唯一碳源和能源的环境中，具有CobB样活性的Pdu蛋白确保了prpBCDE操纵子的表达。由于该Pdu蛋白的合成依赖于1，2-丙二醇的可用性，该细胞通过使cobB位于pduoperon之外并且其表达独立于1，2-丙二醇而解决了在缺乏1，2-丙二醇的环境中所面临的问题，其中丙酸盐是唯一的碳源和能量源。目前，还不清楚CobB和Pdu蛋白如何影响prpBCDE表达。
Expression of theprpBCDEoperon ofSalmonella typhimuriumLT2 required (i) the synthesis of propionyl-coenzyme A (CoA) by the PrpE protein or the acetyl-CoA-synthesizing systems of the cell and (ii) the synthesis of 2-methylcitrate from propionyl-CoA and oxaloacetate by the PrpC protein. We propose that either 2-methylcitrate or a derivative of it signals the presence of propionate in the environment. This as yet unidentified signal is thought to serve as a coregulator of the activity of PrpR, the member of the sigma-54 family of transcriptional activators needed for activation ofprpBCDEtranscription. The CobB protein was also required for expression of theprpBCDEoperon, but its role is less well understood. Expression of theprpBCDEoperon incobBmutants was restored to wild-type levels upon induction of the propanediol utilization (pdu) operon by 1,2-propanediol. This effect did not require catabolism of 1,2-propanediol, suggesting that a Pdu protein, not a catabolite of 1,2-propanediol, was responsible for the observed effect. We explain the existence of these redundant functions in terms of metabolic pathway integration. In an environment with 1,2-propanediol as the sole carbon and energy source, expression of theprpBCDEoperon is ensured by the Pdu protein that has CobB-like activity. Since synthesis of this Pdu protein depends on the availability of 1,2-propanediol, the cell solves the problem faced in an environment devoid of 1,2-propanediol where propionate is the sole carbon and energy source by havingcobBlocated outside of thepduoperon and its expression independent of 1,2-propanediol. At present, it is unclear how the CobB and Pdu proteins affectprpBCDEexpression.