The general PTS component HPr determines the preference for glucose over mannitol.
The general PTS component HPr determines the preference for glucose over mannitol.
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DOI：
10.1038/srep43431
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发表时间：
2017-02-22
影响因子：
4.6
通讯作者：
Seok YJ
中科院分区：
文献类型：
--
作者：
Choe M;Park YH;Lee CR;Kim YR;Seok YJ
糖的优先利用是生物系统中普遍存在的现象。葡萄糖通常是各种生物体中最优选的碳源，特别是在细菌中，其中葡萄糖通过磷酸烯醇丙酮酸：糖磷酸转移酶系统（PTS）被摄取。目前提出的肠道细菌（包括大肠杆菌）对葡萄糖的偏好模型。大肠杆菌中的酶活性严格依赖于葡萄糖特异性PTS组分酶IIAGlc（EIIAGlc）的磷酸化状态。然而，在革兰氏阴性菌中PTS糖之间的偏好机制在很大程度上是未知的。在这里，我们表明，葡萄糖的偏好超过另一个PTS糖，甘露醇，是绝对依赖于一般的PTS组分HPr，但不依赖于EIIAGlc，在E。杆菌去磷酸化的HPr在葡萄糖转运过程中积累，并与甘露醇操纵子调节剂MtlR相互作用，以增强其阻遏活性。这种相互作用阻断了甘露醇对甘露醇操纵子表达的诱导作用，并导致甘露醇利用的抑制。
Preferential sugar utilization is a widespread phenomenon in biological systems. Glucose is usually the most preferred carbon source in various organisms, especially in bacteria where it is taken up via the phosphoenolpyruvate:sugar phosphotransferase system (PTS). The currently proposed model for glucose preference over non-PTS sugars in enteric bacteria including E. coli is strictly dependent on the phosphorylation state of the glucose-specific PTS component, enzyme IIAGlc (EIIAGlc). However, the mechanism of the preference among PTS sugars is largely unknown in Gram-negative bacteria. Here, we show that glucose preference over another PTS sugar, mannitol, is absolutely dependent on the general PTS component HPr, but not on EIIAGlc, in E. coli. Dephosphorylated HPr accumulates during the transport of glucose and interacts with the mannitol operon regulator, MtlR, to augment its repressor activity. This interaction blocks the inductive effect of mannitol on the mannitol operon expression and results in the inhibition of mannitol utilization.