Protonation drives the conformational switch in the multidrug transporter LmrP.
Protonation drives the conformational switch in the multidrug transporter LmrP.
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DOI：
10.1038/nchembio.1408
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发表时间：
2014-02
影响因子：
14.8
通讯作者：
Govaerts C
中科院分区：
文献类型：
--
作者：
Masureel M;Martens C;Stein RA;Mishra S;Ruysschaert JM;Mchaourab HS;Govaerts C
主要易化因子超家族的多药反向转运蛋白将质子转运与细胞毒性分子的排出偶联。这些转运蛋白的转运循环和耦合的结构基础的基础上的构象变化尚未阐明。在此，我们利用广泛的双电子电子共振测量来揭示LmrP的构象平衡，LmrP是一种来自L.乳酸，并研究质子和配体如何改变这种平衡，使运输。我们发现，转运蛋白之间的开关向外开放和向外关闭的构象取决于特定的酸性残基形成跨膜质子化中继的质子化状态。我们的数据可以被框在一个模型中的运输，其中底物结合启动运输周期通过打开细胞外侧。随后的质子化的膜嵌入的酸性残基诱导底物释放到细胞外侧，并触发级联的构象变化，在质子释放到细胞内侧结束。
Multidrug antiporters of the Major Facilitator Superfamily couple proton translocation to the extrusion of cytotoxic molecules. The conformational changes that underlie the transport cycle and the structural basis of coupling of these transporters have not been elucidated. Here we utilized extensive Double Electron Electron Resonance measurements to uncover the conformational equilibrium of LmrP, a multidrug transporter from L. lactis, and to investigate how protons and ligands shift this equilibrium to enable transport. We find that the transporter switches between outward-open and outward-closed conformations depending on the protonation states of specific acidic residues forming a transmembrane protonation relay. Our data can be framed in a model of transport wherein substrate binding initiates the transport cycle by opening the extracellular side. Subsequent protonation of membrane-embedded acidic residues induces substrate release to the extracellular side and triggers a cascade of conformational changes that concludes in proton release to the intracellular side.