PERMEABILITY PROPERTIES OF A LARGE GATED CHANNEL WITHIN THE FERRIC ENTEROBACTIN RECEPTOR, FEPA
PERMEABILITY PROPERTIES OF A LARGE GATED CHANNEL WITHIN THE FERRIC ENTEROBACTIN RECEPTOR, FEPA
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DOI：
10.1073/pnas.90.22.10653
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发表时间：
1993-11-15
影响因子：
11.1
通讯作者：
KLEBBA, PE
中科院分区：
文献类型：
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作者：
LIU, J;RUTZ, JM;KLEBBA, PE
FepA是铁载体铁肠杆菌素的大肠杆菌外膜受体蛋白。先前在体内进行的研究表明，FepA和其他TonB依赖性外膜蛋白通过门控通道机制转运配体。为了证实和扩展这些发现，我们已经确定了FepA通道在体外的渗透性，通过测量脂质体溶胀实验中的FepA通道的亲水性非电解质的扩散速率。与孔蛋白一样，FepA缺失突变体DELTARV显示出对寡糖的大小依赖性渗透性，表明它形成了非特异性的亲水孔。与OmpF和其他E.而DELTARV蛋白脂质体主要转运水苏糖（666 Da）和铁色素（740 Da）。这些数据，和其他摄取结果与一系列的麦芽糖糊精的增加的大小，证实了通道域的存在，在FepA内是相当大的比OmpF型孔。这些结果代表了TonB依赖性受体蛋白的通道功能的重建，并确立了FepA含有在大肠杆菌中表征的最大通道。大肠杆菌外膜。
FepA is an Escherichia coli outer membrane receptor protein for the siderophore ferric enterobactin. Prior studies conducted in vivo suggested that FepA and other TonB-dependent outer membrane proteins transport ligands by a gated-channel mechanism. To corroborate and extend these findings we have determined the permeability properties of the FepA channel in vitro, by measuring the diffusion rates of hydrophilic nonelectrolytes through the FepA channel in liposome swelling experiments. Like porins, the FepA deletion mutant DELTARV showed a size-dependent permeability to oligosaccharides, indicating that it forms a nonspecific, hydrophilic pore. Unlike OmpF and other E. coli porins, however, DELTARV proteoliposomes transported stachyose (666 Da) and ferrichrome (740 Da). These data, and other uptake results with a series of maltodextrins of increasing size, confirm the existence of a channel domain within FepA that is considerably larger than OmpF-type pores. These results represent a reconstitution of the channel function of a TonB-dependent receptor protein and establish that FepA contains the largest channel that has been characterized in the E. coli outer membrane.