2.A.6.2.40
MDR pump, AdeABC (Acinetobacter drug efflux B = AdeB).It exports chloramphenicol and tetracycline (Hassan et al., 2011), but also confers resistance to meropenem, tigecycline and ceftazidime (Peleg et al. 2007; Provasi Cardoso et al. 2016). Morgan et al. 2021 reported six structures of the trimeric AdeB multidrug efflux pump in the presence of ethidium bromide using single-particle cryo-EM. These structures allowed them to directly observe various novel conformational states of the AdeB trimer. The transmembrane region of trimeric AdeB can associate with formation of a trimeric assembly or dissociated into "dimer plus monomer" and "monomer plus monomer plus monomer" configurations. A single AdeB protomer can simultaneously anchor a number of ethidium ligands, and different AdeB protomers can bind ethidium molecules simultaneously. A drug transport mechanism was proposed that involves multiple multidrug-binding sites and various transient states of the AdeB membrane protein. This suggests that each AdeB protomer within the trimer binds and exports drugs independently (Morgan et al. 2021).