Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan.
Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto, 606-8501, Japan.
Nat Commun. 2019 Jan 8;10(1):88. doi: 10.1038/s41467-018-08007-x.
P-glycoprotein extrudes a large variety of xenobiotics from the cell, thereby protecting tissues from their toxic effects. The machinery underlying unidirectional multidrug pumping remains unknown, largely due to the lack of high-resolution structural information regarding the alternate conformational states of the molecule. Here we report a pair of structures of homodimeric P-glycoprotein: an outward-facing conformational state with bound nucleotide and an inward-facing apo state, at resolutions of 1.9 Å and 3.0 Å, respectively. Features that can be clearly visualized at this high resolution include ATP binding with octahedral coordination of Mg; an inner chamber that significantly changes in volume with the aid of tight connections among transmembrane helices (TM) 1, 3, and 6; a glutamate-arginine interaction that stabilizes the outward-facing conformation; and extensive interactions between TM1 and TM3, a property that distinguishes multidrug transporters from floppases. These structural elements are proposed to participate in the mechanism of the transporter.
P-糖蛋白将多种外源物质从细胞内排出，从而保护组织免受其毒性影响。由于缺乏关于分子的交替构象状态的高分辨率结构信息，单向多药物泵送的机制在很大程度上仍不清楚。在这里，我们报告了一对同源二聚体 P-糖蛋白的结构：一个结合核苷酸的外向构象状态和一个无核苷酸的内向状态，分辨率分别为 1.9 Å 和 3.0 Å。在这个高分辨率下，可以清晰地看到包括 ATP 与 Mg 的八面体配位结合；一个内腔，其体积随跨膜螺旋 (TM) 1、3 和 6 之间的紧密连接而显著变化；一个谷氨酸-精氨酸相互作用，稳定外向构象；以及 TM1 和 TM3 之间的广泛相互作用，这种特性将多药物转运体与 floppases 区分开来。这些结构元素被提议参与转运体的机制。
