Tyrosine Phosphorylation of the UDP-Glucose Dehydrogenase of Escherichia coli Is at the Crossroads of Colanic Acid Synthesis and Polymyxin Resistance
Tyrosine Phosphorylation of the UDP-Glucose Dehydrogenase of Escherichia coli Is at the Crossroads of Colanic Acid Synthesis and Polymyxin Resistance
复制标题
DOI：
10.1371/journal.pone.0003053
复制
发表时间：
2008-08-25
期刊：
影响因子：
3.7
通讯作者：
Grangeasse, Christophe
中科院分区：
文献类型：
--
作者：
Lacour, Soline;Bechet, Emmanuelle;Grangeasse, Christophe
背景资料：近年来，一类特殊的新型细菌酶，命名为BY-激酶，已被证明催化蛋白质酪氨酸磷酸化。这些酶与它们的真核生物对应物没有结构和功能上的相似性，并且迄今为止，只有少数BY激酶的底物被表征。BY-激酶已被证明参与各种生理过程。尽管如此，我们仍处于确定它们在细菌细胞中的重要性的早期阶段。在大肠杆菌中，两种BY-激酶，Wzc和Etk，已经被生物化学表征。Wzc已显示在体外磷酸化UDP-葡萄糖脱氢酶Ugd。Ugd不仅参与胞外多糖的生物合成，而且参与UDP-4-氨基-4-脱氧-L-阿拉伯糖的产生，UDP-4-氨基-4-脱氧-L-阿拉伯糖是一种使E.方法学/主要发现：在这里，我们研究了Ugd磷酸化的作用。我们首先在体内证实了Wzc对Ugd的磷酸化作用，并且我们证明了Ugd也被Etk磷酸化，Etk是在大肠杆菌中鉴定的另一种BY激酶。杆菌酪氨酸71（Tyr 71）被表征为被Wzc和Etk两者磷酸化的Ugd位点。然后评估Tyr 71磷酸化对Ugd活性的调节作用，发现Tyr 71突变阻止Ugd通过磷酸化活化。此外，通过Wzc或Etk的Ugd磷酸化显示出用于不同的生理目的。发现Wzc对Ugd的磷酸化参与调节胞外多糖colanic acid的量，而Etk介导的Ugd磷酸化似乎参与E.结论/意义：Ugd磷酸化似乎是在两个不同的生物合成途径之间的交界处，说明酪氨酸磷酸化在细菌生理学中的调节潜力。
Background: In recent years, an idiosyncratic new class of bacterial enzymes, named BY-kinases, has been shown to catalyze protein-tyrosine phosphorylation. These enzymes share no structural and functional similarities with their eukaryotic counterparts and, to date, only few substrates of BY-kinases have been characterized. BY-kinases have been shown to participate in various physiological processes. Nevertheless, we are at a very early stage of defining their importance in the bacterial cell. In Escherichia coli, two BY-kinases, Wzc and Etk, have been characterized biochemically. Wzc has been shown to phosphorylate the UDP-glucose dehydrogenase Ugd in vitro. Not only is Ugd involved in the biosynthesis of extracellular polysaccharides, but also in the production of UDP-4-amino-4-deoxy-L-arabinose, a compound that renders E. coli resistant to cationic antimicrobial peptides.Methodology/Principal Findings: Here, we studied the role of Ugd phosphorylation. We first confirmed in vivo the phosphorylation of Ugd by Wzc and we demonstrated that Ugd is also phosphorylated by Etk, the other BY-kinase identified in E. coli. Tyrosine 71 (Tyr71) was characterized as the Ugd site phosphorylated by both Wzc and Etk. The regulatory role of Tyr71 phosphorylation on Ugd activity was then assessed and Tyr71 mutation was found to prevent Ugd activation by phosphorylation. Further, Ugd phosphorylation by Wzc or Etk was shown to serve distinct physiological purposes. Phosphorylation of Ugd by Wzc was found to participate in the regulation of the amount of the exopolysaccharide colanic acid, whereas Etk-mediated Ugd phosphorylation appeared to participate in the resistance of E. coli to the antibiotic polymyxin.Conclusions/Significance: Ugd phosphorylation seems to be at the junction between two distinct biosynthetic pathways, illustrating the regulatory potential of tyrosine phosphorylation in bacterial physiology.