Autophosphorylation of the Escherichia coli protein kinase wzc regulates tyrosine phosphorylation of Ugd, a UDP-glucose dehydrogenase
Autophosphorylation of the Escherichia coli protein kinase wzc regulates tyrosine phosphorylation of Ugd, a UDP-glucose dehydrogenase
复制标题
DOI：
10.1074/jbc.m305134200
复制
发表时间：
2003-10-10
影响因子：
4.8
通讯作者：
Doublet, P
中科院分区：
文献类型：
--
作者：
Grangeasse, C;Obadia, B;Doublet, P
在许多革兰氏阴性和革兰氏阳性细菌中，观察到参与胞外多糖和衣壳多糖生物合成和运输的蛋白酪氨酸激酶(PTKs)的自磷酸化。然而，除了它们自身的磷酸化作用外，人们对这些蛋白质修饰酶所针对的其他底物知之甚少。在这里，我们提出的证据表明，大肠杆菌的蛋白酪氨酸激酶Wzc能够磷酸化一种内源性酶，UDP葡萄糖脱氢酶(UGD)，该酶参与胞外多糖可乐酸的合成。WZC对UGD的磷酸化过程被先前WZC在酪氨酸569上的自磷酸化所刺激。UGD的磷酸化实际上发生在酪氨酸上，并导致其脱氢酶活性显著增加。此外，已知能有效地使WZC去磷酸化的磷酸酪氨酸蛋白磷酸酶WZB对UGD的去磷酸化只表现出很低的效果(如果有)。这些数据与最近观察到的另外两个UDP-葡萄糖脱氢酶也被证明是被革兰氏阳性细菌枯草芽孢杆菌中的PTK磷酸化有关。对革兰氏阴性菌和革兰氏阳性菌PTK活性的比较分析表明，它们受到不同机制的调节，分别涉及激酶的自动磷酸化或它们与膜蛋白激活剂的相互作用。
Autophosphorylation of protein-tyrosine kinases (PTKs) involved in exopolysaccharide and capsular polysaccharide biosynthesis and transport has been observed in a number of Gram-negative and Gram-positive bacteria. However, besides their own phosphorylation, little is known about other substrates targeted by these protein-modifying enzymes. Here, we present evidence that the protein-tyrosine kinase Wzc of Escherichia coli is able to phosphorylate an endogenous enzyme, UDPglucose dehydrogenase (Ugd), which participates in the synthesis of the exopolysaccharide colanic acid. The process of phosphorylation of Ugd by Wzc was shown to be stimulated by previous autophosphorylation of Wzc on tyrosine 569. The phosphorylation of Ugd was demonstrated to actually occur on tyrosine and result in a significant increase of its dehydrogenase activity. In addition, the phosphotyrosine-protein phosphatase Wzb, which is known to effectively dephosphorylate Wzc, exhibited only a low effect, if any, on the dephosphorylation of Ugd. These data were related to the recent observation that two other UDP-glucose dehydrogenases have been also shown to be phosphorylated by a PTK in the Gram-positive bacterium Bacillus subtilis. Comparative analysis of the activities of PTKs from Gram-negative and Gram-positive bacteria showed that they are regulated by different mechanisms that involve, respectively, either the autophosphorylation of kinases or their interaction with a membrane protein activator.