Cryoelectron Microscopy Structures of AdeB Illuminate Mechanisms of Simultaneous Binding and Exporting of Substrates.
Cryoelectron Microscopy Structures of AdeB Illuminate Mechanisms of Simultaneous Binding and Exporting of Substrates.
复制标题
作者：
Morgan CE;Glaza P;Leus IV;Trinh A;Su CC;Cui M;Zgurskaya HI;Yu EW
鲍曼不动杆菌是一种革兰氏阴性杆菌，已成为全球对抗生素耐药性最高的细菌之一。这些高度耐药菌株和其他机会性病原体中的多药外排是感染性疾病药物治疗失败的主要原因。鲍曼不动杆菌中最典型的多药外排系统是流行的不动杆菌药物外排B(ADEB)泵，它是耐药结节细胞分裂(RND)超家族的成员。在这里，我们用单粒子低温电子显微镜(Cryo-EM)报道了溴化乙锭存在下的三聚体ADEB多药外排泵的六种结构。这些结构使我们能够直接观察到ADEB三聚体的各种新的构象状态，包括ADEB的跨膜区可以与形成三聚体组装或解离成“二聚体+单体”和“单体+单体+单体”构型。我们还发现，单个ADEB原基可以同时锚定多个乙锭配体，不同的ADEB原基可以同时结合乙锭分子。结合分子动力学(MD)模拟，我们揭示了ADEB膜蛋白的多个药物结合部位和各种瞬时状态的药物转运机制。我们的数据表明，三聚体中的每个ADEB原体能独立结合和输出药物。
Acinetobacter baumannii is a Gram-negative pathogen that has emerged as one of the most highly antibiotic-resistant bacteria worldwide. Multidrug efflux within these highly drug-resistant strains and other opportunistic pathogens is a major cause of failure of drug-based treatments of infectious diseases. The best-characterized multidrug efflux system in A. baumannii is the prevalent Acinetobacter drug efflux B (AdeB) pump, which is a member of the resistance-nodulation-cell division (RND) superfamily. Here, we report six structures of the trimeric AdeB multidrug efflux pump in the presence of ethidium bromide using single-particle cryoelectron microscopy (cryo-EM). These structures allow us to directly observe various novel conformational states of the AdeB trimer, including the transmembrane region of trimeric AdeB can be associated with form a trimer assembly or dissociated into “dimer plus monomer” and “monomer plus monomer plus monomer” configurations. We also discover that a single AdeB protomer can simultaneously anchor a number of ethidium ligands and that different AdeB protomers can bind ethidium molecules simultaneously. Combined with molecular dynamics (MD) simulations, we reveal a drug transport mechanism that involves multiple multidrug-binding sites and various transient states of the AdeB membrane protein. Our data suggest that each AdeB protomer within the trimer binds and exports drugs independently.