Phosphorylation of tyrosine 474 of the enteropathogenic Escherichia coli (EPEC) Tir receptor molecule is essential for actin nucleating activity and is preceded by additional host modifications
Phosphorylation of tyrosine 474 of the enteropathogenic Escherichia coli (EPEC) Tir receptor molecule is essential for actin nucleating activity and is preceded by additional host modifications
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DOI：
10.1046/j.1365-2958.1999.01265.x
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发表时间：
1999-02-01
影响因子：
3.6
通讯作者：
Kenny, B
中科院分区：
文献类型：
--
作者：
Kenny, B
肠致病性大肠杆菌（EPEC）Tir蛋白在宿主细胞中变得酪氨酸磷酸化并显示表观分子量增加。Tir与EPEC外膜蛋白（intimin）的相互作用触发粘附细菌下方的肌动蛋白成核。肠出血性E. coli O 157：H7（EHEC）Tir分子不被酪氨酸磷酸化。在本文中，Tir酪氨酸磷酸化被证明是必不可少的肌动蛋白成核活性，但不是在靶细胞中观察到的表观分子量的增加。酪氨酸磷酸化在Tir分子量变化中没有作用，表明另外的宿主修饰。Tir中间体的分析表明，酪氨酸非依赖性修饰的功能，以指导Tir的正确插入从细胞质到宿主膜。缺失分析鉴定了参与易位、与宿主膜结合、修饰和抗体识别的Tir结构域。发现内膜结合Tir内的55个氨基酸区域（TIBA），拓扑和序列分析表明其位于细胞外环中。同源TIBA序列存在于整合素中，其也结合内膜蛋白。总的来说，本研究提供了明确的证据，酪氨酸磷酸化的重要性，EPEC Tir功能，并揭示了EPEC和EHEC的致病性的差异，数据还提出了一种机制，Tir插入到宿主膜，以及提供线索的方式intimin-integrin相互作用。
The enteropathogenic Escherichia coli (EPEC) Tir protein becomes tyrosine phosphorylated in host cells and displays an increase in apparent molecular mass. The interaction of Tir with the EPEC outer membrane protein, intimin, triggers actin nucleation beneath the adherent bacteria. The enterohaemorrhagic E. coli O157:H7 (EHEC) Tir molecule is not tyrosine phosphorylated. In this paper, Tir tyrosine phosphorylation is shown to be essential for actin nucleation activity, but not for the increase in apparent molecular mass observed in target cells. Tyrosine phosphorylation had no role in Tir molecular mass shift, indicating additional host modifications. Analysis of Tir intermediates indicates that tyrosine-independent modification functions to direct Tir's correct insertion from the cytoplasm into the host membrane. Deletion analysis identified Tir domains participating in translocation, association with the host membrane, modification and antibody recognition. Intimin was found to bind a 55-amino-acid region (TIBA) within Tir that topological and sequence analysis suggests is located in an extracellular loop. Homologous TIBA sequences exist in integrins, which also bind intimin. Collectively, this study provides definitive evidence for the importance of tyrosine phosphorylation for EPEC Tir function and reveals differences in the pathogenicity of EPEC and EHEC, The data also suggest a mechanism for Tir insertion into the host membrane, as well as providing clues to the mode of intimin-integrin interaction.