Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX, 77030, USA.
Jiangsu Province Key Laboratory of Anesthesiology and Jiangsu Province Key Laboratory of Anesthesia and Analgesia Application, Xuzhou Medical University, Xuzhou, Jiangsu, 221004, China.
Nat Commun. 2019 Jun 14;10(1):2635. doi: 10.1038/s41467-019-10512-6.
Multidrug efflux pumps actively expel a wide range of toxic substrates from the cell and play a major role in intrinsic and acquired drug resistance. In Gram-negative bacteria, these pumps form tripartite assemblies that span the cell envelope. However, the in situ structure and assembly mechanism of multidrug efflux pumps remain unknown. Here we report the in situ structure of the Escherichia coli AcrAB-TolC multidrug efflux pump obtained by electron cryo-tomography and subtomogram averaging. The fully assembled efflux pump is observed in a closed state under conditions of antibiotic challenge and in an open state in the presence of AcrB inhibitor. We also observe intermediate AcrAB complexes without TolC and discover that AcrA contacts the peptidoglycan layer of the periplasm. Our data point to a sequential assembly process in living bacteria, beginning with formation of the AcrAB subcomplex and suggest domains to target with efflux pump inhibitors.
多药外排泵主动将多种毒性底物从细胞中排出，在固有和获得性耐药中起主要作用。在革兰氏阴性菌中，这些泵形成跨细胞膜的三联体组装。然而，多药外排泵的原位结构和组装机制仍然未知。在这里，我们通过电子 cryo-tomography 和子断层平均法报道了 Escherichia coli AcrAB-TolC 多药外排泵的原位结构。在抗生素挑战条件下，观察到完全组装的外排泵处于关闭状态，而在存在 AcrB 抑制剂的情况下，观察到处于打开状态。我们还观察到没有 TolC 的中间 AcrAB 复合物，并发现 AcrA 与周质层的肽聚糖层接触。我们的数据指向活细菌中的顺序组装过程，首先形成 AcrAB 亚复合物，并提出了针对外排泵抑制剂的靶标域。
