Ligand-gated diffusion across the bacterial outer membrane
Ligand-gated diffusion across the bacterial outer membrane
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DOI：
10.1073/pnas.1018532108
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发表时间：
2011-06-21
影响因子：
11.1
通讯作者：
van den Berg, Bert
中科院分区：
文献类型：
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作者：
Lepore, Bryan W.;Indic, Mridhu;van den Berg, Bert
配体门控通道是一类在原核生物和真核生物中具有重要功能的膜蛋白，它通过与小分子化学信使的结合形成底物转运途径。尽管它们广泛存在，但在革兰氏阴性菌的外膜(OM)中尚未发现配体门控通道。在这里，我们利用体内转运分析、本征色氨酸荧光和X射线结晶学表明，高亲和力(亚微摩尔)底物与来自大肠杆菌的OM长链脂肪酸转运蛋白Fad1结合导致N端的构象变化，从而为底物扩散打开了一条通道。来自大肠杆菌的OM长链脂肪酸转运体Fadl是一种独特的OM扩散驱动的转运范例，其中β-桶膜蛋白内的配基门控是通道形成的先决条件。
Ligand-gated channels, in which a substrate transport pathway is formed as a result of the binding of a small-molecule chemical messenger, constitute a diverse class of membrane proteins with important functions in prokaryotic and eukaryotic organisms. Despite their widespread nature, no ligand-gated channels have yet been found within the outer membrane (OM) of Gram-negative bacteria. Here we show, using in vivo transport assays, intrinsic tryptophan fluorescence and X-ray crystallography, that high-affinity (submicromolar) substrate binding to the OM long-chain fatty acid transporter FadL from Escherichia coli causes conformational changes in the N terminus that open up a channel for substrate diffusion. The OM long-chain fatty acid transporter FadL from E. coli is a unique paradigm for OM diffusion-driven transport, in which ligand gating within a beta-barrel membrane protein is a prerequisite for channel formation.