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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Escherichia coli enzyme IIA~(Ntr) regulates the K~+ transporter TrkA
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Escherichia coli enzyme IIA~(Ntr) regulates the K~+ transporter TrkA

机译：大肠杆菌酶IIA〜（Ntr）调节K〜+转运蛋白TrkA

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摘要

The maintenance of ionic homeostasis in response to changes in the environment is essential for all living cells. Although there are still many important questions concerning the role of the major monovalent cation K~+, cytoplasmic K~+ in bacteria is required for diverse processes. Here, we show that enzyme IIA~(Ntr) (EIIA~(Ntr)) of the nitrogen-metabolic phosphotransferase system interacts with and regulates the Escherichia coli K~+ transporter TrkA. Previously we reported that an E. coli K-12 mutant in the ptsN gene encoding EIIA~(Ntr) was extremely sensitive to growth inhibition by leucine or leucine-containing peptides (LCPs). This sensitivity was due to the requirement of the dephosphorylated form of EIIA~(Ntr) for the derepression of ilvBN expression. Whereas the ptsN mutant is extremely sensitive to LCPs, a ptsN trkA double mutant is as resistant as WT. Furthermore, the sensitivity of the ptsN mutant to LCPs decreases as the K~+ level in culture media is lowered. We demonstrate that dephosphorylated EIIA~(Ntr), but not its phosphor-ylated form, forms a tight complex with TrkA that inhibits the accumulation of high intracellular concentrations of K~+. High cellular K~+ levels in a ptsN mutant promote the sensitivity of E. coli K-12 to leucine or LCPs by inhibiting both the expression of ilvBN and the activity of its gene products. Here, we delineate the similarity of regulatory mechanisms for the paralogous carbon and nitrogen phosphotransferase systems. Dephosphorylated EIIA~(Glc) regulates a variety of transport systems for carbon sources, whereas dephosphorylated EIIA~(Ntr) regulates the transport system for K~+, which has global effects related to nitrogen metabolism.
机译：响应环境变化而维持离子稳态对于所有活细胞都是必不可少的。尽管仍然存在关于主要的单价阳离子K +的作用的许多重要问题，但是细菌的胞质K +对于多种过程是必需的。在此，我们显示了氮代谢磷酸转移酶系统的酶IIA〜（Ntr）（EIIA〜（Ntr））与大肠杆菌K +转运蛋白TrkA相互作用并对其进行调节。先前我们报道了编码EIIA_（Ntr）的ptsN基因中的大肠杆菌K-12突变体对亮氨酸或含亮氨酸的肽（LCP）的生长抑制极为敏感。这种敏感性是由于EILV〜（Ntr）的去磷酸化形式需要抑制ilvBN表达。 ptsN突变体对LCP极为敏感，而ptsN trkA双突变体与WT一样具有抗性。此外，随着培养基中钾离子水平的降低，ptsN突变体对LCPs的敏感性降低。我们证明，去磷酸化的EIIA〜（Ntr），而不是其磷酸化的形式，与TrkA形成紧密的复合物，从而抑制高细胞内K〜+浓度的积累。 ptsN突变体中的高细胞K〜+水平通过抑制ilvBN的表达及其基因产物的活性，从而提高了大肠杆菌K-12对亮氨酸或LCP的敏感性。在这里，我们描绘了类似的碳和氮磷酸转移酶系统的调节机制的相似性。脱磷的EIIA〜（Glc）调节碳源的多种转运系统，而脱磷的EIIA〜（Ntr）调节K〜+的转运系统，这与氮代谢有关。

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