Structures of the multidrug exporter AcrB reveal a proximal multisite drug-binding pocket
Structures of the multidrug exporter AcrB reveal a proximal multisite drug-binding pocket
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DOI：
10.1038/nature10641
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发表时间：
2011-12-22
期刊：
影响因子：
64.8
通讯作者：
Yamaguchi, Akihito
中科院分区：
文献类型：
--
作者：
Nakashima, Ryosuke;Sakurai, Keisuke;Yamaguchi, Akihito
AcrB及其同系物是革兰氏阴性菌中的主要多药转运蛋白（1-6），在抗生素耐药性中很重要（7，8）。AcrB是一种同源三聚体，与外膜通道TolC（11，12）和膜融合蛋白AcrA（13，14）形成三重复合物（9，10）。米诺环素和多柔比星已显示与结合单体的苯丙氨酸簇区域结合（15）。在这里，我们报告的晶体结构的AcrB绑定到高分子量药物利福平和红霉素。这些药物与通路单体结合，结合位点位于近端多位点结合口袋中，其通过Phe-617环与苯丙氨酸簇区域（远端口袋）分开。我们的结构表明，有两个离散的多位点结合口袋沿着分子内通道。高分子量药物首先在进入状态下结合到近端口袋，然后通过蠕动机制被迫进入结合状态下的远端口袋，所述蠕动机制涉及亚结构域运动，包括Phe-617环的移位。相比之下，低分子量药物，如米诺环素和阿霉素，通过近端口袋没有特异性结合，并立即结合到远端口袋。两个离散的，高容量的多位点结合口袋的存在下，有助于显着广泛的底物识别的AcrB。
AcrB and its homologues are the principal multidrug transporters in Gram-negative bacteria(1-6) and are important in antibiotic drug tolerance(7,8). AcrB is a homotrimer that acts as a tripartite complex(9,10) with the outer membrane channel TolC(11,12) and the membrane fusion protein AcrA(13,14). Minocycline and doxorubicin have been shown to bind to the phenylalanine cluster region of the binding monomer(15). Here we report the crystal structures of AcrB bound to the high-molecular-mass drugs rifampicin and erythromycin. These drugs bind to the access monomer, and the binding sites are located in the proximal multisite binding pocket, which is separated from the phenylalanine cluster region (distal pocket) by the Phe-617 loop. Our structures indicate that there are two discrete multisite binding pockets along the intramolecular channel. High-molecular-mass drugs first bind to the proximal pocket in the access state and are then forced into the distal pocket in the binding state by a peristaltic mechanism involving subdomain movements that include a shift of the Phe-617 loop. By contrast, low-molecular-mass drugs, such as minocycline and doxorubicin, travel through the proximal pocket without specific binding and immediately bind to the distal pocket. The presence of two discrete, high-volume multisite binding pockets contributes to the remarkably broad substrate recognition of AcrB.